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Sample records for compact hyperbolic spaces

  1. Nonlinear sigma models with compact hyperbolic target spaces

    NASA Astrophysics Data System (ADS)

    Gubser, Steven; Saleem, Zain H.; Schoenholz, Samuel S.; Stoica, Bogdan; Stokes, James

    2016-06-01

    We explore the phase structure of nonlinear sigma models with target spaces corresponding to compact quotients of hyperbolic space, focusing on the case of a hyperbolic genus-2 Riemann surface. The continuum theory of these models can be approximated by a lattice spin system which we simulate using Monte Carlo methods. The target space possesses interesting geometric and topological properties which are reflected in novel features of the sigma model. In particular, we observe a topological phase transition at a critical temperature, above which vortices proliferate, reminiscent of the Kosterlitz-Thouless phase transition in the O(2) model [1, 2]. Unlike in the O(2) case, there are many different types of vortices, suggesting a possible analogy to the Hagedorn treatment of statistical mechanics of a proliferating number of hadron species. Below the critical temperature the spins cluster around six special points in the target space known as Weierstrass points. The diversity of compact hyperbolic manifolds suggests that our model is only the simplest example of a broad class of statistical mechanical models whose main features can be understood essentially in geometric terms.

  2. Analytic vortex solutions on compact hyperbolic surfaces

    NASA Astrophysics Data System (ADS)

    Maldonado, Rafael; Manton, Nicholas S.

    2015-06-01

    We construct, for the first time, abelian Higgs vortices on certain compact surfaces of constant negative curvature. Such surfaces are represented by a tessellation of the hyperbolic plane by regular polygons. The Higgs field is given implicitly in terms of Schwarz triangle functions and analytic solutions are available for certain highly symmetric configurations.

  3. Can rodents conceive hyperbolic spaces?

    PubMed Central

    Urdapilleta, Eugenio; Troiani, Francesca; Stella, Federico; Treves, Alessandro

    2015-01-01

    The grid cells discovered in the rodent medial entorhinal cortex have been proposed to provide a metric for Euclidean space, possibly even hardwired in the embryo. Yet, one class of models describing the formation of grid unit selectivity is entirely based on developmental self-organization, and as such it predicts that the metric it expresses should reflect the environment to which the animal has adapted. We show that, according to self-organizing models, if raised in a non-Euclidean hyperbolic cage rats should be able to form hyperbolic grids. For a given range of grid spacing relative to the radius of negative curvature of the hyperbolic surface, such grids are predicted to appear as multi-peaked firing maps, in which each peak has seven neighbours instead of the Euclidean six, a prediction that can be tested in experiments. We thus demonstrate that a useful universal neuronal metric, in the sense of a multi-scale ruler and compass that remain unaltered when changing environments, can be extended to other than the standard Euclidean plane. PMID:25948611

  4. On compactness estimates for hyperbolic systems of conservation laws

    NASA Astrophysics Data System (ADS)

    Ancona, Fabio; Glass, Olivier; Nguyen, Khai T.

    2015-11-01

    We study the compactness in $L^{1}_{loc}$ of the semigroup mapping $(S_t)_{t > 0}$ defining entropy weak solutions of general hyperbolic systems of conservation laws in one space dimension. We establish a lower estimate for the Kolmogorov $\\varepsilon$-entropy of the image through the mapping $S_t$ of bounded sets in $L^{1}\\cap L^\\infty$, which is of the same order $1/\\varepsilon$ as the ones established by the authors for scalar conservation laws. We also provide an upper estimate of order $1/\\varepsilon$ for the Kolmogorov $\\varepsilon$-entropy of such sets in the case of Temple systems with genuinely nonlinear characteristic families, that extends the same type of estimate derived by De Lellis and Golse for scalar conservation laws with convex flux. As suggested by Lax, these quantitative compactness estimates could provide a measure of the order of "resolution" of the numerical methods implemented for these equations.

  5. D-branes on spaces stratified fibered over hyperbolic orbifolds

    NASA Astrophysics Data System (ADS)

    Bytsenko, A. A.; Chaichian, M.; Guimarães, M. E. X.

    2014-09-01

    We apply the methods of homology and K-theory for branes wrapping spaces stratified fibered over hyperbolic orbifolds. In addition, we discuss the algebraic K-theory of any discrete co-compact Lie group in terms of appropriate homology and Atiyah-Hirzebruch type spectral sequence with its nontrivial lift to K-homology. We emphasize the fact that the physical D-branes properties are completely transparent within the mathematical framework of K-theory. We derive criteria for D-brane stability in the case of strongly virtually negatively curved groups. We show that branes wrapping spaces stratified fibered over hyperbolic orbifolds carry charge structure and change the additive structural properties in K-homology.

  6. Gauge theories on hyperbolic spaces and dual wormhole instabilities

    SciTech Connect

    Buchel, Alex

    2004-09-15

    We study supergravity duals of strongly coupled four-dimensional gauge theories formulated on compact quotients of hyperbolic spaces. The resulting background geometries are represented by Euclidean wormholes, which complicate establishing the precise gauge theory/string theory correspondence dictionary. These backgrounds suffer from the nonperturbative instabilities arising from the D3D3-bar pair-production in the background four-form potential. We discuss conditions for suppressing this Schwingerlike instability. We find that Euclidean wormholes arising in this construction develop a naked singularity before they can be stabilized.

  7. Duality between preferential attachment and static networks on hyperbolic spaces

    NASA Astrophysics Data System (ADS)

    Ferretti, L.; Cortelezzi, M.; Mamino, M.

    2014-02-01

    There is a complex relation between the mechanism of preferential attachment, scale-free degree distributions and hyperbolicity in complex networks. In fact, both preferential attachment and hidden hyperbolic spaces often generate scale-free networks. We show that there is actually a duality between a class of growing spatial networks based on preferential attachment on the sphere and a class of static random networks on the hyperbolic plane. Both classes of networks have the same scale-free degree distribution as the Barabasi-Albert model. As a limit of this correspondence, the Barabasi-Albert model is equivalent to a static random network on an hyperbolic space with infinite curvature.

  8. Vacua and correlators in hyperbolic de Sitter space

    NASA Astrophysics Data System (ADS)

    Dimitrakopoulos, Fotios V.; Kabir, Laurens; Mosk, Benjamin; Parikh, Maulik; van der Schaar, Jan Pieter

    2015-06-01

    We study the power- and bi-spectrum of vacuum fluctuations in a hyperbolic section of de Sitter space, comparing two states of physical interest: the Bunch-Davies and hyperbolic vacuum. We introduce a one-parameter family of de Sitter hyperbolic sections and their natural vacua, and identify a limit in which it reduces to the planar section and the corresponding Bunch-Davies vacuum state. Selecting the Bunch-Davies vacuum for a massless scalar field implies a mixed reduced density matrix in a hyperbolic section of de Sitter space. We stress that in the Bunch-Davies state the hyperbolic de Sitter n-point correlation functions have to match the planar de Sitter n-point correlation functions. The expressions for the planar and hyperbolic Bunch-Davies correlation functions only appear different because of the transformation from planar to hyperbolic coordinates. Initial state induced deviations from the standard inflationary predictions are instead obtained by considering the pure hyperbolic vacuum, as we verify explicitly by computing the power- and bi-spectrum. For the bi-spectrum in the hyperbolic vacuum we find that the corrections as compared to the standard Bunch-Davies result are not enhanced in specific momentum configurations and strongly suppressed for momenta large compared to the hyperbolic curvature scale. We close with some final remarks, in particular regarding the implications of these results for more realistic inflationary bubble scenarios.

  9. Compact hyperbolic extra dimensions: branes, kaluza-klein modes, and cosmology

    PubMed

    Kaloper; March-Russell; Starkman; Trodden

    2000-07-31

    We reconsider theories with low gravitational (or string) scale M(*) where Newton's constant is generated via new large-volume spatial dimensions, while standard model states are localized to a 3-brane. Utilizing compact hyperbolic manifolds we show that the spectrum of Kaluza-Klein modes is radically altered. This allows the early Universe to evolve normally up to substantial temperatures, and completely negates the astrophysical constraints on M(*). Furthermore, an exponential hierarchy between the usual Planck scale and the true fundamental scale of physics can emerge with only O(1) coefficients. The linear size of the internal space remains small. The proposal has striking testable signatures. PMID:10991441

  10. A remark on geometric desingularization of a non-hyperbolic point using hyperbolic space

    NASA Astrophysics Data System (ADS)

    Kuehn, Christian

    2016-06-01

    A steady state (or equilibrium point) of a dynamical system is hyperbolic if the Jacobian at the steady state has no eigenvalues with zero real parts. In this case, the linearized system does qualitatively capture the dynamics in a small neighborhood of the hyperbolic steady state. However, one is often forced to consider non-hyperbolic steady states, for example in the context of bifurcation theory. A geometric technique to desingularize non-hyperbolic points is the blow-up method. The classical case of the method is motivated by desingularization techniques arising in algebraic geometry. The idea is to blow up the steady state to a sphere or a cylinder. In the blown-up space, one is then often able to gain additional hyperbolicity at steady states. The method has also turned out to be a key tool to desingularize multiple time scale dynamical systems with singularities. In this paper, we discuss an explicit example of the blow-up method where we replace the sphere in the blow-up by hyperbolic space. It is shown that the calculations work in the hyperbolic space case as for the spherical case. This approach may be even slightly more convenient if one wants to work with directional charts. Hence, it is demonstrated that the sphere should be viewed as an auxiliary object in the blow-up construction. Other smooth manifolds are also natural candidates to be inserted at steady states. Furthermore, we conjecture several problems where replacing the sphere could be particularly useful, i.e., in the context of singularities of geometric flows, for avoiding compactification, and generating 'interior' steady states.

  11. Linking and Causality in Globally Hyperbolic Space-times

    NASA Astrophysics Data System (ADS)

    Chernov (Tchernov), Vladimir V.; Rudyak, Yuli B.

    2008-04-01

    The classical linking number lk is defined when link components are zero homologous. In [15] we constructed the affine linking invariant alk generalizing lk to the case of linked submanifolds with arbitrary homology classes. Here we apply alk to the study of causality in Lorentzian manifolds. Let M m be a spacelike Cauchy surface in a globally hyperbolic space-time ( X m+1, g). The spherical cotangent bundle ST * M is identified with the space mathcal N of all null geodesics in ( X, g). Hence the set of null geodesics passing through a point xin X gives an embedded ( m-1)-sphere mathfrak S_x in mathcal N=ST^*M called the sky of x. Low observed that if the link (mathfrak S_x, mathfrak S_y) is nontrivial, then x,yin X are causally related. This observation yielded a problem (communicated by R. Penrose) on the V. I. Arnold problem list [3,4] which is basically to study the relation between causality and linking. Our paper is motivated by this question. The spheres mathfrak S_x are isotopic to the fibers of (ST^*M)^{2m-1}to M^m. They are nonzero homologous and the classical linking number lk(mathfrak S_x, mathfrak S_y) is undefined when M is closed, while alk(mathfrak S_x, mathfrak S_y) is well defined. Moreover, alk(mathfrak S_x, mathfrak S_y)in {mathbb{Z}} if M is not an odd-dimensional rational homology sphere. We give a formula for the increment of alk under passages through Arnold dangerous tangencies. If ( X, g) is such that alk takes values in {mathbb{Z}} and g is conformal to widehat{g} that has all the timelike sectional curvatures nonnegative, then x, yin X are causally related if and only if alk (mathfrak S_x, mathfrak S_y)neq 0 . We prove that if alk takes values in {mathbb{Z}} and y is in the causal future of x, then alk(mathfrak S_x, mathfrak S_y) is the intersection number of any future directed past inextendible timelike curve to y and of the future null cone of x. We show that x, y in a nonrefocussing ( X, g) are causally unrelated if and only if

  12. Visualising very large phylogenetic trees in three dimensional hyperbolic space

    PubMed Central

    Hughes, Timothy; Hyun, Young; Liberles, David A

    2004-01-01

    Background Common existing phylogenetic tree visualisation tools are not able to display readable trees with more than a few thousand nodes. These existing methodologies are based in two dimensional space. Results We introduce the idea of visualising phylogenetic trees in three dimensional hyperbolic space with the Walrus graph visualisation tool and have developed a conversion tool that enables the conversion of standard phylogenetic tree formats to Walrus' format. With Walrus, it becomes possible to visualise and navigate phylogenetic trees with more than 100,000 nodes. Conclusion Walrus enables desktop visualisation of very large phylogenetic trees in 3 dimensional hyperbolic space. This application is potentially useful for visualisation of the tree of life and for functional genomics derivatives, like The Adaptive Evolution Database (TAED). PMID:15117420

  13. Exact moduli space metrics for hyperbolic vortex polygons

    SciTech Connect

    Krusch, S.; Speight, J. M.

    2010-02-15

    Exact metrics on some totally geodesic submanifolds of the moduli space of static hyperbolic N-vortices are derived. These submanifolds, denoted as {sigma}{sub n,m}, are spaces of C{sub n}-invariant vortex configurations with n single vortices at the vertices of a regular polygon and m=N-n coincident vortices at the polygon's center. The geometric properties of {sigma}{sub n,m} are investigated, and it is found that {sigma}{sub n,n-1} is isometric to the hyperbolic plane of curvature -(3{pi}n){sup -1}. The geodesic flow on {sigma}{sub n,m} and a geometrically natural variant of geodesic flow recently proposed by Collie and Tong ['The dynamics of Chern-Simons vortices', Phys. Rev. D Part. Fields Gravit. Cosmol. 78, 065013 (2008);e-print arXiv:hep-th/0805.0602] are analyzed in detail.

  14. Convergence theorems for generalized nonexpansive multivalued mappings in hyperbolic spaces.

    PubMed

    Kim, Jong Kyu; Pathak, Ramesh Prasad; Dashputre, Samir; Diwan, Shailesh Dhar; Gupta, Rajlaxmi

    2016-01-01

    In this paper, we establish the existence of a fixed point for generalized nonexpansive multivalued mappings in hyperbolic spaces and we prove some [Formula: see text]-convergence and strong convergence theorems for the iterative scheme proposed by Chang et al. (Appl Math Comp 249:535-540, 2014) to approximate a fixed point for generalized nonexpansive multivalued mapping under suitable conditions. Our results are the extension and improvements of the recent well-known results announced in the current literature. PMID:27386356

  15. Space-time methods for hyperbolic conservation laws

    SciTech Connect

    Lowrie, R.B.; Roe, P.L.; Leer, B.V.

    1996-12-31

    Two challenges for computational fluid dynamics are problems that involve wave propagation over long times and problems with a wide range of amplitude scales. An example with both of these characteristics is the propagation and generation of acoustic waves, where the mean-flow amplitude scales are typically orders-of-magnitude larger than those of the generated acoustics. Other examples include vortex evolution and the direct simulation of turbulence. All these problems require greater than second-order accuracy, whereas for nonlinear equations, most current methods are at best second- order accurate. Of the higher-order (greater than second-order) methods that exist, most are tailored to high-spatial resolution, coupled with time integrators that are only second or third-order accurate. But for wave phenomena, time accuracy is as important as spatial accuracy. One property of successful second-order methods is that they attempt to be faithful to the physics of hyperbolic problems. To develop higher-order methods, particularly for unsteady problems, it is tempting to violate this philosophy. Typically, higher accuracy is obtained by increasing the size of the update stencil. Instead our aim is to develop time-accurate methods that minimize the size of the update stencil. The approach in this study is strongly motivated by the physics of hyperbolic conservation laws. Specifically, we insist that a numerical method`s discrete zone of dependence should only be slightly larger (for stability) than the physical zone of dependence. A time-accurate method has been developed that is based on the Discontinuous Galerkin method. In deriving the method, the idea of compactness has been strictly followed. That is, that the discrete domain of dependence should contain a minimum amount of data outside of the physical domain of dependence. For any order-of-accuracy, the method is stable for Courant numbers less than 1, satisfies an entropy condition, and a minimization property.

  16. Experimental compact space power station

    NASA Astrophysics Data System (ADS)

    Pospisil, M.; Pospisilova, L.; Hanzelka, Z.; Prochazka, M.

    1980-09-01

    A hexagonal structure of 1-km diameter and a weight of 500 metric tons situated at geosynchronous orbit is proposed for testing a space power station of 64 MW peak power in operation and for evaluating materials, means and methods needed for production of large stations. In this compact space power station, solar blankets and microwave sources are situated on one supporting structure, thus saving a lot of auxiliary parts, but the exploitation of solar elements is 3.3 times lower than for an earlier concept.

  17. Invariant distributions on compact homogeneous spaces

    SciTech Connect

    Gorbatsevich, V V

    2013-12-31

    In this paper, we study distributions on compact homogeneous spaces, including invariant distributions and also distributions admitting a sub-Riemannian structure. We first consider distributions of dimension 1 and 2 on compact homogeneous spaces. After this, we study the cases of compact homogeneous spaces of dimension 2, 3, and 4 in detail. Invariant distributions on simply connected compact homogeneous spaces are also treated. Bibliography: 18 titles.

  18. Strings in compact cosmological spaces

    NASA Astrophysics Data System (ADS)

    Craps, Ben; Evnin, Oleg; Konechny, Anatoly

    2013-10-01

    We confront the problem of giving a fundamental definition to perturbative string theory in spacetimes with totally compact space (taken to be a torus for simplicity, though the nature of the problem is very general) and non-compact time. Due to backreaction induced by the presence of even a single string quantum, the usual formulation of perturbative string theory in a fixed classical background is infrared-divergent at all subleading orders in the string coupling, and needs to be amended. The problem can be seen as a closed string analogue of D0-brane recoil under an impact by closed strings (a situation displaying extremely similar infrared divergences). Inspired by the collective coordinate treatment of the D0-brane recoil, whereby the translational modes of the D0-brane are introduced as explicit dynamical variables in the path integral, we construct a similar formalism for the case of string-induced gravitational backreaction, in which the spatially uniform modes of the background fields on the compact space are quantized explicitly. The formalism can equally well be seen as an ultraviolet completion of a minisuperspace quantum cosmology with string degrees of freedom. We consider the amplitudes for the universe to have two cross-sections with specified spatial properties and string contents, and show (at the first non-trivial order) that they are finite within our formalism.

  19. Orienteering in knowledge spaces: the hyperbolic geometry of Wikipedia Mathematics.

    PubMed

    Leibon, Gregory; Rockmore, Daniel N

    2013-01-01

    In this paper we show how the coupling of the notion of a network with directions with the adaptation of the four-point probe from materials testing gives rise to a natural geometry on such networks. This four-point probe geometry shares many of the properties of hyperbolic geometry wherein the network directions take the place of the sphere at infinity, enabling a navigation of the network in terms of pairs of directions: the geodesic through a pair of points is oriented from one direction to another direction, the pair of which are uniquely determined. We illustrate this in the interesting example of the pages of Wikipedia devoted to Mathematics, or "The MathWiki." The applicability of these ideas extends beyond Wikipedia to provide a natural framework for visual search and to prescribe a natural mode of navigation for any kind of "knowledge space" in which higher order concepts aggregate various instances of information. Other examples would include genre or author organization of cultural objects such as books, movies, documents or even merchandise in an online store. PMID:23844017

  20. Compaction of Space Mission Wastes

    NASA Technical Reports Server (NTRS)

    Fisher, John; Pisharody, Suresh; Wignarajah, K.

    2004-01-01

    The current solid waste management system employed on the International Space Station (ISS) consists of compaction, storage, and disposal. Wastes such plastic food packaging and trash are compacted manually and wrapped in duct tape footballs by the astronauts. Much of the waste is simply loaded either into the empty Russian Progress vehicle for destruction on reentry or into Shuttle for return to Earth. This manual method is wasteful of crew time and does not transition well to far term missions. Different wastes onboard spacecraft vary considerably in their characteristics and in the appropriate method of management. In advanced life support systems for far term missions, recovery of resources such as water from the wastes becomes important. However waste such as plastic food packaging, which constitutes a large fraction of solid waste (roughly 21% on ISS, more on long duration missions), contains minimal recoverable resource. The appropriate management of plastic waste is waste stabilization and volume minimization rather than resource recovery. This paper describes work that has begun at Ames Research Center on development of a heat melt compactor that can be used on near term and future missions, that can minimize crew interaction, and that can handle wastes with a significant plastic composition. The heat melt compactor takes advantage of the low melting point of plastics to compact plastic materials using a combination of heat and pressure. The US Navy has demonstrated successful development of a similar unit for shipboard application. Ames is building upon the basic approach demonstrated by the Navy to develop an advanced heat melt type compactor for space mission type wastes.

  1. Nonoscillatory Central Schemes for Hyperbolic Systems of Conservation Laws in Three-Space Dimensions

    PubMed Central

    Guarendi, Andrew N.; Chandy, Abhilash J.

    2013-01-01

    We extend a family of high-resolution, semidiscrete central schemes for hyperbolic systems of conservation laws to three-space dimensions. Details of the schemes, their implementation, and properties are presented together with results from several prototypical applications of hyperbolic conservation laws including a nonlinear scalar equation, the Euler equations of gas dynamics, and the ideal magnetohydrodynamic equations. Parallel scaling analysis and grid-independent results including contours and isosurfaces of density and velocity and magnetic field vectors are shown in this study, confirming the ability of these types of solvers to approximate the solutions of hyperbolic equations efficiently and accurately. PMID:24058287

  2. Nonoscillatory central schemes for hyperbolic systems of conservation laws in three-space dimensions.

    PubMed

    Guarendi, Andrew N; Chandy, Abhilash J

    2013-01-01

    We extend a family of high-resolution, semidiscrete central schemes for hyperbolic systems of conservation laws to three-space dimensions. Details of the schemes, their implementation, and properties are presented together with results from several prototypical applications of hyperbolic conservation laws including a nonlinear scalar equation, the Euler equations of gas dynamics, and the ideal magnetohydrodynamic equations. Parallel scaling analysis and grid-independent results including contours and isosurfaces of density and velocity and magnetic field vectors are shown in this study, confirming the ability of these types of solvers to approximate the solutions of hyperbolic equations efficiently and accurately. PMID:24058287

  3. Motion Among Random Obstacles on a Hyperbolic Space

    NASA Astrophysics Data System (ADS)

    Orsingher, Enzo; Ricciuti, Costantino; Sisti, Francesco

    2016-02-01

    We consider the motion of a particle along the geodesic lines of the Poincaré half-plane. The particle is specularly reflected when it hits randomly-distributed obstacles that are assumed to be motionless. This is the hyperbolic version of the well-known Lorentz Process studied in the Euclidean context. We analyse the limit in which the density of the obstacles increases to infinity and the size of each obstacle vanishes: under a suitable scaling, we prove that our process converges to a Markovian process, namely a random flight on the hyperbolic manifold.

  4. SRB measures for a class of partially hyperbolic attractors in Hilbert spaces

    NASA Astrophysics Data System (ADS)

    Lian, Zeng; Liu, Peidong; Lu, Kening

    2016-07-01

    In this paper, we study the existence of SRB measures and their properties for infinite dimensional dynamical systems in a Hilbert space. We show several results including (i) if the system has a partially hyperbolic attractor with nontrivial finite dimensional unstable directions, then it has at least one SRB measure; (ii) if the attractor is uniformly hyperbolic and the system is topological mixing and the splitting is Hölder continuous, then there exists a unique SRB measure which is mixing; (iii) if the attractor is uniformly hyperbolic and the system is non-wondering and the splitting is Hölder continuous, then there exist at most finitely many SRB measures; (iv) for a given hyperbolic measure, there exist at most countably many ergodic components whose basin contains an observable set.

  5. Fast community detection based on sector edge aggregation metric model in hyperbolic space

    NASA Astrophysics Data System (ADS)

    Wang, Zuxi; Li, Qingguang; Xiong, Wei; Jin, Fengdong; Wu, Yao

    2016-06-01

    By studying the edge aggregation characteristic of nodes in hyperbolic space, Sector Edge Aggregation Metric (SEAM) model is proposed and theoretically proved in this paper. In hyperbolic disk SEAM model determines the minimum angular range of a sector which possesses the maximal edge aggregation of nodes. The set of nodes within such sector has dense internal links, which corresponds with the characteristic of community structure. Based on SEAM model, we propose a fast community detection algorithm called Greedy Optimization Modularity Algorithm (GOMA) which employs greedy optimization strategy and hyperbolic coordinates. GOMA firstly divides initial communities according to the quantitative results of sector edge aggregation given by SEAM and the nodes' hyperbolic coordinates, then based on greedy optimization strategy, only merges the two angular neighboring communities in hyperbolic disk to optimize the network modularity function, and consequently obtains high-quality community detection. The strategies of initial community partition and merger in hyperbolic space greatly improve the speed of searching the most optimal modularity. Experimental results indicate that GOMA is able to detect out high-quality community structure in synthetic and real networks, and performs better when applied to the large-scale and dense networks with strong clustering.

  6. Some remarks on the current status of the control theory of single space dimension hyperbolic systems

    NASA Technical Reports Server (NTRS)

    Russell, D. L.

    1983-01-01

    Various aspects of the control theory of hyperbolic systems, including controllability, stabilization, control canonical form theory, etc., are reviewed. To allow a unified and not excessively technical treatment, attention is restricted to the case of a single space variable. A newly developed procedure of canonical augmentation is discussed.

  7. Orienteering in Knowledge Spaces: The Hyperbolic Geometry of Wikipedia Mathematics

    PubMed Central

    Leibon, Gregory; Rockmore, Daniel N.

    2013-01-01

    In this paper we show how the coupling of the notion of a network with directions with the adaptation of the four-point probe from materials testing gives rise to a natural geometry on such networks. This four-point probe geometry shares many of the properties of hyperbolic geometry wherein the network directions take the place of the sphere at infinity, enabling a navigation of the network in terms of pairs of directions: the geodesic through a pair of points is oriented from one direction to another direction, the pair of which are uniquely determined. We illustrate this in the interesting example of the pages of Wikipedia devoted to Mathematics, or “The MathWiki.” The applicability of these ideas extends beyond Wikipedia to provide a natural framework for visual search and to prescribe a natural mode of navigation for any kind of “knowledge space” in which higher order concepts aggregate various instances of information. Other examples would include genre or author organization of cultural objects such as books, movies, documents or even merchandise in an online store. PMID:23844017

  8. The Fujita exponent for the Cauchy problem in the hyperbolic space

    NASA Astrophysics Data System (ADS)

    Bandle, Catherine; Pozio, Maria Assunta; Tesei, Alberto

    It is well known that the heat kernel in the hyperbolic space has a different behavior for large times than the one in the Euclidean space. The main purpose of this paper is to study its effect on the positive solutions of Cauchy problems with power nonlinearities. Existence and non-existence results for local solutions are derived. Emphasis is put on their long time behavior and on Fujita's phenomenon. To have the same situation as for the Cauchy problem in R, namely finite time blow up for all solutions if the exponent is smaller than a critical value and existence of global solutions only for powers above the critical exponent, we must introduce a weight depending exponentially on the time. In this respect the situation is similar to problems in bounded domains with Dirichlet boundary conditions. Important tools are estimates for the heat kernel in the hyperbolic space and comparison principles.

  9. Global embedding of the Kerr black hole event horizon into hyperbolic 3-space

    SciTech Connect

    Gibbons, G. W.; Herdeiro, C. A. R.; Rebelo, C.

    2009-08-15

    An explicit global and unique isometric embedding into hyperbolic 3-space, H{sup 3}, of an axi-symmetric 2-surface with Gaussian curvature bounded below is given. In particular, this allows the embedding into H{sup 3} of surfaces of revolution having negative, but finite, Gaussian curvature at smooth fixed points of the U(1) isometry. As an example, we exhibit the global embedding of the Kerr-Newman event horizon into H{sup 3}, for arbitrary values of the angular momentum. For this example, considering a quotient of H{sup 3} by the Picard group, we show that the hyperbolic embedding fits in a fundamental domain of the group up to a slightly larger value of the angular momentum than the limit for which a global embedding into Euclidean 3-space is possible. An embedding of the double-Kerr event horizon is also presented, as an example of an embedding that cannot be made global.

  10. Hyperbolic-metamaterial antennas for broadband enhancement of dipole emission to free space

    SciTech Connect

    Valagiannopoulos, C. A.; Mirmoosa, M. S.; Nefedov, I. S.; Tretyakov, S. A.; Simovski, C. R.

    2014-10-28

    Dipole emitters used in nano optics and nanophotonics (e.g., fluorescent molecules or quantum dots) are weak radiators and thus detecting the radiation of a single emitter gets possible only if it is significantly enhanced. For this enhancement, one often utilizes resonant nanoantennas (Purcell's effect); this method, however, requires the exact knowledge of source location and radiation frequency which constitute a significant drawback. One known possibility for broadband location-insensitive radiation enhancement is to use a layer of the so-called hyperbolic metamaterial. However, the enhanced radiated energy is mainly directed into the volume of the lossy medium, where it is lost to heating. In this work, we suggest specific shapes of macroscopic hyperbolic metamaterial samples to open radiation windows for enhanced radiation to free space. We show that hyperbolic media slabs with properly shaped macroscopic grooves convert the evanescent waves produced by a dipole into waves traveling in free space, which results in the enhancement of useful radiation by one to two orders of magnitude. That level of enhancement of radiation into free-space which is also wideband and of non-resonant nature has not been reported up to now. These results may open possibilities for realization of broadband and directive antennas, where the primary radiators are randomly positioned fluorescent molecules or quantum dots.

  11. Efficient embedding of complex networks to hyperbolic space via their Laplacian

    NASA Astrophysics Data System (ADS)

    Alanis-Lobato, Gregorio; Mier, Pablo; Andrade-Navarro, Miguel A.

    2016-07-01

    The different factors involved in the growth process of complex networks imprint valuable information in their observable topologies. How to exploit this information to accurately predict structural network changes is the subject of active research. A recent model of network growth sustains that the emergence of properties common to most complex systems is the result of certain trade-offs between node birth-time and similarity. This model has a geometric interpretation in hyperbolic space, where distances between nodes abstract this optimisation process. Current methods for network hyperbolic embedding search for node coordinates that maximise the likelihood that the network was produced by the afore-mentioned model. Here, a different strategy is followed in the form of the Laplacian-based Network Embedding, a simple yet accurate, efficient and data driven manifold learning approach, which allows for the quick geometric analysis of big networks. Comparisons against existing embedding and prediction techniques highlight its applicability to network evolution and link prediction.

  12. Compact Deep-Space Optical Communications Transceiver

    NASA Technical Reports Server (NTRS)

    Roberts, W. Thomas; Charles, Jeffrey R.

    2009-01-01

    Deep space optical communication transceivers must be very efficient receivers and transmitters of optical communication signals. For deep space missions, communication systems require high performance well beyond the scope of mere power efficiency, demanding maximum performance in relation to the precious and limited mass, volume, and power allocated. This paper describes the opto-mechanical design of a compact, efficient, functional brassboard deep space transceiver that is capable of achieving megabyte-per-second rates at Mars ranges. The special features embodied to enhance the system operability and functionality, and to reduce the mass and volume of the system are detailed. System tests and performance characteristics are described in detail. Finally, lessons learned in the implementation of the brassboard design and suggestions for improvements appropriate for a flight prototype are covered.

  13. Abstract State-Space Models for a Class of Linear Hyperbolic Systems of Balance Laws

    NASA Astrophysics Data System (ADS)

    Bartecki, Krzysztof

    2015-12-01

    The paper discusses and compares different abstract state-space representations for a class of linear hyperbolic systems defined on a one-dimensional spatial domain. It starts with their PDE representation in both weakly and strongly coupled forms. Next, the homogeneous state equation including the unbounded formal state operator is presented. Based on the semigroup approach, some results of well-posedness and internal stability are given. The boundary and observation operators are introduced, assuming a typical configuration of boundary inputs as well as pointwise observations of the state variables. Consequently, the homogeneous state equation is extended to the so-called boundary control state/signal form. Next, the classical additive statespace representation involving (A, B, C)-triple of state, input and output operators is considered. After short discussion on the appropriate Hilbert spaces, state-space equation in the so-called factor form is also presented. Finally, the resolvent of the system state operator A is discussed.

  14. An instability of hyperbolic space under the Yang-Mills flow

    SciTech Connect

    Gegenberg, Jack; Day, Andrew C.; Liu, Haitao; Seahra, Sanjeev S.

    2014-04-15

    We consider the Yang-Mills flow on hyperbolic 3-space. The gauge connection is constructed from the frame-field and (not necessarily compatible) spin connection components. The fixed points of this flow include zero Yang-Mills curvature configurations, for which the spin connection has zero torsion and the associated Riemannian geometry is one of constant curvature. We analytically solve the linearized flow equations for a large class of perturbations to the fixed point corresponding to hyperbolic 3-space. These can be expressed as a linear superposition of distinct modes, some of which are exponentially growing along the flow. The growing modes imply the divergence of the (gauge invariant) perturbative torsion for a wide class of initial data, indicating an instability of the background geometry that we confirm with numeric simulations in the partially compactified case. There are stable modes with zero torsion, but all the unstable modes are torsion-full. This leads us to speculate that the instability is induced by the torsion degrees of freedom present in the Yang-Mills flow.

  15. Time-stable boundary conditions for finite-difference schemes solving hyperbolic systems: Methodology and application to high-order compact schemes

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Gottlieb, David; Abarbanel, Saul

    1993-01-01

    We present a systematic method for constructing boundary conditions (numerical and physical) of the required accuracy, for compact (Pade-like) high-order finite-difference schemes for hyperbolic systems. First, a roper summation-by-parts formula is found for the approximate derivative. A 'simultaneous approximation term' (SAT) is then introduced to treat the boundary conditions. This procedure leads to time-stable schemes even in the system case. An explicit construction of the fourth-order compact case is given. Numerical studies are presented to verify the efficacy of the approach.

  16. Time-stable boundary conditions for finite-difference schemes solving hyperbolic systems: Methodology and application to high-order compact schemes

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Gottlieb, David; Abarbanel, Saul

    1994-01-01

    We present a systematic method for constructing boundary conditions (numerical and physical) of the required accuracy, for compact (Pade-like) high-order finite-difference schemes for hyperbolic systems. First a proper summation-by-parts formula is found for the approximate derivative. A 'simultaneous approximation term' is then introduced to treat the boundary conditions. This procedure leads to time-stable schemes even in the system case. An explicit construction of the fourth-order compact case is given. Numerical studies are presented to verify the efficacy of the approach.

  17. Efficient embedding of complex networks to hyperbolic space via their Laplacian

    PubMed Central

    Alanis-Lobato, Gregorio; Mier, Pablo; Andrade-Navarro, Miguel A.

    2016-01-01

    The different factors involved in the growth process of complex networks imprint valuable information in their observable topologies. How to exploit this information to accurately predict structural network changes is the subject of active research. A recent model of network growth sustains that the emergence of properties common to most complex systems is the result of certain trade-offs between node birth-time and similarity. This model has a geometric interpretation in hyperbolic space, where distances between nodes abstract this optimisation process. Current methods for network hyperbolic embedding search for node coordinates that maximise the likelihood that the network was produced by the afore-mentioned model. Here, a different strategy is followed in the form of the Laplacian-based Network Embedding, a simple yet accurate, efficient and data driven manifold learning approach, which allows for the quick geometric analysis of big networks. Comparisons against existing embedding and prediction techniques highlight its applicability to network evolution and link prediction. PMID:27445157

  18. Efficient embedding of complex networks to hyperbolic space via their Laplacian.

    PubMed

    Alanis-Lobato, Gregorio; Mier, Pablo; Andrade-Navarro, Miguel A

    2016-01-01

    The different factors involved in the growth process of complex networks imprint valuable information in their observable topologies. How to exploit this information to accurately predict structural network changes is the subject of active research. A recent model of network growth sustains that the emergence of properties common to most complex systems is the result of certain trade-offs between node birth-time and similarity. This model has a geometric interpretation in hyperbolic space, where distances between nodes abstract this optimisation process. Current methods for network hyperbolic embedding search for node coordinates that maximise the likelihood that the network was produced by the afore-mentioned model. Here, a different strategy is followed in the form of the Laplacian-based Network Embedding, a simple yet accurate, efficient and data driven manifold learning approach, which allows for the quick geometric analysis of big networks. Comparisons against existing embedding and prediction techniques highlight its applicability to network evolution and link prediction. PMID:27445157

  19. On quantum symmetries of compact metric spaces

    NASA Astrophysics Data System (ADS)

    Chirvasitu, Alexandru

    2015-08-01

    An action of a compact quantum group on a compact metric space (X, d) is (D)-isometric if the distance function is preserved by a diagonal action on X × X. In this study, we show that an isometric action in this sense has the following additional property: the corresponding action on the algebra of continuous functions on X by the convolution semigroup of probability measures on the quantum group contracts Lipschitz constants. In other words, it is isometric in another sense due to Li, Quaegebeur, and Sabbe, which partially answers a question posed by Goswami. We also introduce other possible notions of isometric quantum actions in terms of the Wasserstein p-distances between probability measures on X for p ≥ 1, which are used extensively in optimal transportation. Indeed, all of these definitions of quantum isometry belong to a hierarchy of implications, where the two described above lie at the extreme ends of the hierarchy. We conjecture that they are all equivalent.

  20. Gravitational catalysis of chiral and color symmetry breaking of quark matter in hyperbolic space

    SciTech Connect

    Ebert, D.; Tyukov, A. V.; Zhukovsky, V. Ch.

    2009-10-15

    We study the dynamical breaking of chiral and color symmetries of dense quark matter in the ultrastatic hyperbolic spacetime R x H{sup 3} in the framework of an extended Nambu-Jona-Lasinio model. On the basis of analytical expressions for chiral and color condensates as functions of curvature and temperature, the phenomenon of dimensional reduction and gravitational catalysis of symmetry breaking in strong gravitational field is demonstrated in the regime of weak coupling constants. In the case of strong couplings it is shown that curvature leads to small corrections to the flat-space values of condensate and thus enhances the symmetry breaking effects. Finally, using numerical calculations phase transitions under the influence of chemical potential and negative curvature are considered and the phase portrait of the system is constructed.

  1. Isoperimetric inequality on conformally hyperbolic manifolds

    SciTech Connect

    Kesel'man, V M

    2003-04-30

    It is shown that on an arbitrary non-compact Riemannian manifold of conformally hyperbolic type the isoperimetric inequality can be taken by a conformal change of the metric to the same canonical linear form as in the case of the standard hyperbolic Lobachevskii space. Both the absolute isoperimetric inequality and the relative one (for manifolds with boundary) are obtained. This work develops the results and methods of a joint paper with Zorich, in which the absolute isoperimetric inequality was obtained under a certain additional condition; the resulting statements are definitive in a certain sense.

  2. An Adaptive Finite Difference Method for Hyperbolic Systems in OneSpace Dimension

    SciTech Connect

    Bolstad, John H.

    1982-06-01

    Many problems of physical interest have solutions which are generally quite smooth in a large portion of the region of interest, but have local phenomena such as shocks, discontinuities or large gradients which require much more accurate approximations or finer grids for reasonable accuracy. Examples are atmospheric fronts, ocean currents, and geological discontinuities. In this thesis we develop and partially analyze an adaptive finite difference mesh refinement algorithm for the initial boundary value problem for hyperbolic systems in one space dimension. The method uses clusters of uniform grids which can ''move'' along with pulses or steep gradients appearing in the calculation, and which are superimposed over a uniform coarse grid. Such refinements are created, destroyed, merged, separated, recursively nested or moved based on estimates of the local truncation error. We use a four-way linked tree and sequentially allocated deques (double-ended queues) to perform these operations efficiently. The local truncation error in the interior of the region is estimated using a three-step Richardson extrapolation procedure, which can also be considered a deferred correction method. At the boundaries we employ differences to estimate the error. Our algorithm was implemented using a portable, extensible Fortran preprocessor, to which we added records and pointers. The method is applied to three model problems: the first order wave equation, the second order wave equation, and the inviscid Burgers equation. For the first two model problems our algorithm is shown to be three to five times more efficient (in computing time) than the use of a uniform coarse mesh, for the same accuracy. Furthermore, to our knowledge, our algorithm is the only one which adaptively treats time-dependent boundary conditions for hyperbolic systems.

  3. Magnetic hyperbolic optical metamaterials

    NASA Astrophysics Data System (ADS)

    Kruk, Sergey S.; Wong, Zi Jing; Pshenay-Severin, Ekaterina; O'Brien, Kevin; Neshev, Dragomir N.; Kivshar, Yuri S.; Zhang, Xiang

    2016-04-01

    Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light.

  4. Magnetic hyperbolic optical metamaterials.

    PubMed

    Kruk, Sergey S; Wong, Zi Jing; Pshenay-Severin, Ekaterina; O'Brien, Kevin; Neshev, Dragomir N; Kivshar, Yuri S; Zhang, Xiang

    2016-01-01

    Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light. PMID:27072604

  5. Magnetic hyperbolic optical metamaterials

    PubMed Central

    Kruk, Sergey S.; Wong, Zi Jing; Pshenay-Severin, Ekaterina; O'Brien, Kevin; Neshev, Dragomir N.; Kivshar, Yuri S.; Zhang, Xiang

    2016-01-01

    Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light. PMID:27072604

  6. Electrodynamics of hyperbolically accelerated charges V. The field of a charge in the Rindler space and the Milne space

    NASA Astrophysics Data System (ADS)

    Eriksen, E.; Grøn, Ø.

    2004-09-01

    We describe the electromagnetic field of a uniformly accelerated charge in its co-moving Rindler frame. It is shown that the electrical field lines coincide with the trajectories of photons. The self force of a charged particle at rest in Rindler space, and the increase of its weight due to its charge, is calculated. The general case of an accelerated charge in Rindler space is also considered. It is shown that the electrical field inside a uniformly charged spherical shell can be used as a measure of it 4-acceleration. A result that has earlier been deduced in a different way by Fugmann and Kretzschmar is confirmed, namely that the intensity of radiation from a point charge instantaneously at rest in an accelerated frame is proportional to the square of the relative acceleration of the charge and the observer. In particular it is shown that a freely falling charge in Rindler space radiates in accordance with Larmor's formula. In this case the radiation energy is taken from the Schott energy. The energy of the electromagnetic field is analysed from the point of view of the Hirayama-separation, which generalizes the Teitelboim-separation to non-inertial frames, of the field in a bound part and an unbound part. A detailed account, with reference to the Rindler frame, of the field energy and particle energy is given for the case of a charge entering and leaving a region with hyperbolic motion. We also consider the electromagnetic field of a uniformly accelerated charge with reference to the Milne frame, which covers a different part of spacetime than the Rindler frame. The radiating part of the electromagnetic field is found in the Milne sector of spacetime.

  7. Effects of Hyperbolic Rotation in Minkowski Space on the Modeling of Plasma Accelerators in a Lorentz Boosted Frame

    SciTech Connect

    Vay, J.-L.; Geddes, C. G. R.; Cormier-Michel, E.; Grote, D. P.

    2010-09-21

    Laser driven plasma accelerators promise much shorter particle accelerators but their development requires detailed simulations that challenge or exceed current capabilities. We report the first direct simulations of stages up to 1 TeV from simulations using a Lorentz boosted calculation frame resulting in a million times speedup, thanks to a frame boost as high as gamma = 1300. Effects of the hyperbolic rotation in Minkowski space resulting from the frame boost on the laser propagation in the plasma is shown to be key in the mitigation of a numerical instability that was limiting previous attempts.

  8. Liquid phase sintered compacts in space

    NASA Technical Reports Server (NTRS)

    Mookherji, T. K.; Mcanelly, W. B.

    1974-01-01

    A model that will explain the effect of gravity on liquid phase sintering was developed. Wetting characteristics and density segregation which are the two important phenomena in liquid phase sintering are considered in the model development. Experiments were conducted on some selected material combinations to study the gravity effects on liquid phase sintering, and to verify the validity of the model. It is concluded that: (1) The surface tension forces acting on solid particles in a one-g environment are not appreciably different from those anticipated in a 0.00001g/g sub 0 (or lower) environment. (2) The capillary forces are dependent on the contact angle, the quantity of the liquid phase, and the distance between solid particles. (3) The pores (i.e., bubbles) do not appear to be driven to the surface by gravity-produced buoyancy forces. (4) The length of time to produce the same degree of settling in a low-gravity environment will be increased significantly. (5) A low gravity environment would appear to offer a unique means of satisfactorily infiltrating a larger and/or complex shaped compact.

  9. A New Time-Space Accurate Scheme for Hyperbolic Problems. 1; Quasi-Explicit Case

    NASA Technical Reports Server (NTRS)

    Sidilkover, David

    1998-01-01

    This paper presents a new discretization scheme for hyperbolic systems of conservations laws. It satisfies the TVD property and relies on the new high-resolution mechanism which is compatible with the genuinely multidimensional approach proposed recently. This work can be regarded as a first step towards extending the genuinely multidimensional approach to unsteady problems. Discontinuity capturing capabilities and accuracy of the scheme are verified by a set of numerical tests.

  10. Fuel systems for compact fast space reactors

    SciTech Connect

    Cox, C.M.; Dutt, D.S.; Karnesky, R.A.

    1983-12-01

    About 200 refractory metal clad ceramic fuel pins have been irradiated in thermal reactors under the 1200 K to 1550 K cladding temperature conditions of primary relevance to space reactors. This paper reviews performance with respect to fissile atom density, operating temperatures, fuel swelling, fission gas release, fuel-cladding compatibility, and consequences of failure. It was concluded that UO/sub 2/ and UN fuels show approximately equal performance potential and that UC fuel has lesser potential. W/Re alloys have performed quite well as cladding materials, and Ta, Nb, and Mo/Re alloys, in conjunction with W diffusion barriers, show good promise. Significant issues to be addressed in the future include high burnup swelling of UN, effects of UO/sub 2/-Li coolant reaction in the event of fuel pin failure, and development of an irradiation performance data base with prototypically configured fuel pins irradiated in a fast neutron flux.

  11. Curved noncommutative tori as Leibniz quantum compact metric spaces

    SciTech Connect

    Latrémolière, Frédéric

    2015-12-15

    We prove that curved noncommutative tori are Leibniz quantum compact metric spaces and that they form a continuous family over the group of invertible matrices with entries in the image of the quantum tori for the conjugation by modular conjugation operator in the regular representation, when this group is endowed with a natural length function.

  12. Curved noncommutative tori as Leibniz quantum compact metric spaces

    NASA Astrophysics Data System (ADS)

    Latrémolière, Frédéric

    2015-12-01

    We prove that curved noncommutative tori are Leibniz quantum compact metric spaces and that they form a continuous family over the group of invertible matrices with entries in the image of the quantum tori for the conjugation by modular conjugation operator in the regular representation, when this group is endowed with a natural length function.

  13. Limit equation for vacuum Einstein constraints with a translational Killing vector field in the compact hyperbolic case

    NASA Astrophysics Data System (ADS)

    Gicquaud, Romain; Huneau, Cécile

    2016-09-01

    We construct solutions to the constraint equations in general relativity using the limit equation criterion introduced in Dahl et al. (2012). We focus on solutions over compact 3-manifolds admitting a S1-symmetry group. When the quotient manifold has genus greater than 2, we obtain strong far from CMC results.

  14. The Tremblay-Turbiner-Winternitz system on spherical and hyperbolic spaces: superintegrability, curvature-dependent formalism and complex factorization

    NASA Astrophysics Data System (ADS)

    Rañada, Manuel F.

    2014-04-01

    The higher order superintegrability of the Tremblay-Turbiner-Winternitz system (related to the harmonic oscillator) is studied on the two-dimensional spherical and hyperbolic spaces, S_\\kappa ^2 (κ > 0) and H_{\\kappa }^2 (κ < 0). The curvature κ is considered as a parameter and all the results are formulated in explicit dependence on κ. The idea is that the additional constant of motion can be factorized as the product of powers of two particular rather simple complex functions (here denoted by Mr and Nϕ). This technique leads to a proof of the superintegrability of the Tremblay-Turbiner-Winternitz system on S_\\kappa ^2 (κ > 0) and H_{\\kappa }^2 (κ < 0), and to the explicit expression of the constants of motion.

  15. Compact, Continuous Beam Cold Atom Clock for Space Applications

    NASA Astrophysics Data System (ADS)

    Buell, Walter

    2000-06-01

    Highly stable atomic frequency standards are of increasing importance for a variety of space applications, ranging from communication to navigation and time transfer to tests of fundamental science. The requirements for an atomic clock vary significantly depending on the application, and for many space systems compactness and robust design are at a premium and stability dominates over absolute accuracy. We report on progress with our design for a compact Cs beam atomic clock suitable for space applications and featuring a cold atomic beam source based on a single beam, conical mirror MOT with a hole at the apex to produce a low velocity high flux atomic beam. This cold atomic beam is then used in a laser-pumped Ramsey clock, with the clock signal derived from either a microwave C-field or alternatively by Raman resonance between the Ramsey fields. The cold atom source produces a continuous beam, which relaxes requirements on the local oscillator as compared with pulsed sources. In order to reduce light shifts from the MOT light and improve signal-to-noise, the atomic beam is optically deflected and transversely cooled upon exiting the MOT's conical reflector. We estimate that the shot-noise-limited stability achievable with this physics package can be two to three orders of magnitude better than current cesium beam atomic clocks used in space applications. We present our latest experimental progress towards a working frequency standard.

  16. On Hyperbolic Embedding of Complements of Divisors and the Limiting Behavior of the Kobayashi-Royden Metric

    NASA Astrophysics Data System (ADS)

    Zaĭdenberg, M. G.

    1986-02-01

    In the following three cases criteria are found for complements of divisors in compact complex manifolds to be hyperbolically embedded in the sense of Kobayashi: for divisors with normal crossings, for arbitrary divisors in complex surfaces, and for unions of hyperplanes in projective space. A criterion is given for two-dimensional polynomial polyhedra to be hyperbolically embedded, and Iitaka's conjecture about conditions for hyperbolicity of the complement of a set of projective lines is confirmed. Upper semicontinuity is proved for the Kobayashi-Royden pseudometrics and Kobayashi-Eisenman pseudovolumes of a family of complex manifolds containing degenerate fibers, and conditions are given under which the hyperbolic length (volume) on the smooth part of a degenerate fiber is the limit of the hyperbolic length (volume) on the nonsingular fibers.Bibliography: 28 titles.

  17. Compact atomic clocks and stabilised laser for space applications

    NASA Astrophysics Data System (ADS)

    Mileti, Gaetano; Affolderbach, Christoph; Matthey-de-l'Endroit, Renaud

    2016-07-01

    We present our developments towards next generation compact vapour-cell based atomic frequency standards using a tunable laser diode instead of a traditional discharge lamp. The realisation of two types of Rubidium clocks addressing specific applications is in progress: high performance frequency standards for demanding applications such as satellite navigation, and chip-scale atomic clocks, allowing further miniaturisation of the system. The stabilised laser source constitutes the main technological novelty of these new standards, allowing a more efficient preparation and interrogation of the atoms and hence an improvement of the clock performances. However, before this key component may be employed in a commercial and ultimately in a space-qualified instrument, further studies are necessary to demonstrate their suitability, in particular concerning their reliability and long-term operation. The talk will present our preliminary investigations on this subject. The stabilised laser diode technology developed for our atomic clocks has several other applications on ground and in space. We will conclude our talk by illustrating this for the example of a recently completed ESA project on a 1.6 microns wavelength reference for a future space-borne Lidar. This source is based on a Rubidium vapour cell providing the necessary stability and accuracy, while a second harmonic generator and a compact optical comb generated from an electro-optic modulator allow to transfer these properties from the Rubidium wavelength (780nm) to the desired spectral range.

  18. A compact 500GHz SIS receiver developed for space observations

    NASA Astrophysics Data System (ADS)

    Liu, D.; Yao, Q. J.; Li, J.; Shi, S. C.

    2011-08-01

    The submillimeter (submm) regime, ranging from 100 to 1000um, is an important frequency band for radio astronomy. A large number of astronomical spectral lines are located in this frequency region. Compared with ground-based observation, which is limited by the atmospheric absorption of signal, space borne platform provides perfect condition for submm observation. Here we introduce some preliminary results for a compact 500GHz SIS (Superconductor- Insulator-Superconductor) heterodyne receiver system developed for future space borne observation. Considering low power consumption requirement for space applications, we adopt a high critical temperature (Tc) NbN/AlN/NbN SIS tunnel junction for the mixer, a key component of the receiver system, which may work at relatively high temperature around 10 K. All the components, including the SIS mixer, HEMT low noise amplifier and optical lens, are assembled into a compact system. The whole system is cooled by a close-cycled 4K cryo-cooler in laboratory and test result shows a good noise performance, less than 250K at the 500GHz band. Detailed simulation and experimental results will be presented in this paper.

  19. Adaptive Controller for Compact Fourier Transform Spectrometer with Space Applications

    NASA Astrophysics Data System (ADS)

    Keymeulen, D.; Yiu, P.; Berisford, D. F.; Hand, K. P.; Carlson, R. W.; Conroy, M.

    2014-12-01

    Here we present noise mitigation techniques developed as part of an adaptive controller for a very compact Compositional InfraRed Interferometric Spectrometer (CIRIS) implemented on a stand-alone field programmable gate array (FPGA) architecture with emphasis on space applications in high radiation environments such as Europa. CIRIS is a novel take on traditional Fourier Transform Spectrometers (FTS) and replaces linearly moving mirrors (characteristic of Michelson interferometers) with a constant-velocity rotating refractor to variably phase shift and alter the path length of incoming light. The design eschews a monochromatic reference laser typically used for sampling clock generation and instead utilizes constant time-sampling via internally generated clocks. This allows for a compact and robust device, making it ideal for spaceborne measurements in the near-IR to thermal-IR band (2-12 µm) on planetary exploration missions. The instrument's embedded microcontroller is implemented on a VIRTEX-5 FPGA and a PowerPC with the aim of sampling the instrument's detector and optical rotary encoder in order to construct interferograms. Subsequent onboard signal processing provides spectral immunity from the noise effects introduced by the compact design's removal of a reference laser and by the radiation encountered during space flight to destinations such as Europa. A variety of signal processing techniques including resampling, radiation peak removal, Fast Fourier Transform (FFT), spectral feature alignment, dispersion correction and calibration processes are applied to compose the sample spectrum in real-time with signal-to-noise-ratio (SNR) performance comparable to laser-based FTS designs in radiation-free environments. The instrument's FPGA controller is demonstrated with the FTS to characterize its noise mitigation techniques and highlight its suitability for implementation in space systems.

  20. Coxeter decompositions of hyperbolic simplexes

    SciTech Connect

    Felikson, A A

    2002-12-31

    A Coxeter decomposition of a polyhedron in a hyperbolic space H{sup n} is a decomposition of it into finitely many Coxeter polyhedra such that any two tiles having a common facet are symmetric with respect to it. The classification of Coxeter decompositions is closely related to the problem of the classification of finite-index subgroups generated by reflections in discrete hyperbolic groups generated by reflections. All Coxeter decompositions of simplexes in the hyperbolic spaces H{sup n} with n>3 are described in this paper.

  1. Compact time- and space-integrating SAR processor: performance analysis

    NASA Astrophysics Data System (ADS)

    Haney, Michael W.; Levy, James J.; Michael, Robert R., Jr.; Christensen, Marc P.

    1995-06-01

    Progress made during the previous 12 months toward the fabrication and test of a flight demonstration prototype of the acousto-optic time- and space-integrating real-time SAR image formation processor is reported. Compact, rugged, and low-power analog optical signal processing techniques are used for the most computationally taxing portions of the SAR imaging problem to overcome the size and power consumption limitations of electronic approaches. Flexibility and performance are maintained by the use of digital electronics for the critical low-complexity filter generation and output image processing functions. The results reported for this year include tests of a laboratory version of the RAPID SAR concept on phase history data generated from real SAR high-resolution imagery; a description of the new compact 2D acousto-optic scanner that has a 2D space bandwidth product approaching 106 sports, specified and procured for NEOS Technologies during the last year; and a design and layout of the optical module portion of the flight-worthy prototype.

  2. Algebraic K-theory of spaces stratified fibered over hyperbolic orbifolds.

    PubMed

    Farrell, F T; Jones, L E

    1986-08-01

    Among other results, we rationally calculate the algebraic K-theory of any discrete cocompact subgroup of a Lie group G, where G is either O(n, 1), U(n, 1), Sp(n, 1), or F(4), in terms of the homology of the double coset space Gamma\\G/K, where K is a maximal cocompact subgroup of G. We obtain the formula K(n)(ZGamma) [unk] [unk] congruent with [unk](i=0) (infinity)H(i)(Gamma\\G/K; [unk](n-i)), where [unk](j) is a stratified system of Q vector spaces over Gamma\\G/K and the vector space [unk](j)(GammagK) corresponding to the double coset GammagK is isomorphic to K(J)(Z(Gamma [unk] gKg(-1))) [unk] Q. Note Gamma [unk] gKg(-1) is a finite subgroup of Gamma. Earlier, a similar formula for discrete cocompact subgroups Gamma of the group of rigid motions of Euclidean space was conjectured by F. T. Farrell and W. C. Hsiang and proven by F. Quinn. PMID:16593733

  3. Algebraic K-theory of spaces stratified fibered over hyperbolic orbifolds

    PubMed Central

    Farrell, F. T.; Jones, L. E.

    1986-01-01

    Among other results, we rationally calculate the algebraic K-theory of any discrete cocompact subgroup of a Lie group G, where G is either O(n, 1), U(n, 1), Sp(n, 1), or F4, in terms of the homology of the double coset space Γ\\G/K, where K is a maximal cocompact subgroup of G. We obtain the formula Kn(ZΓ) [unk] [unk] ≅ [unk]i=0∞Hi(Γ\\G/K; [unk]n-i), where [unk]j is a stratified system of Q vector spaces over Γ\\G/K and the vector space [unk]j(ΓgK) corresponding to the double coset ΓgK is isomorphic to KJ(Z(Γ [unk] gKg-1)) [unk] Q. Note Γ [unk] gKg-1 is a finite subgroup of Γ. Earlier, a similar formula for discrete cocompact subgroups Γ of the group of rigid motions of Euclidean space was conjectured by F. T. Farrell and W. C. Hsiang and proven by F. Quinn. PMID:16593733

  4. Measure of Similarity and Compactness in Competitive Space

    NASA Astrophysics Data System (ADS)

    Zagoruiko, Nikolay

    The given work is devoted to measures of similarity which are used at discovering of empirical regularities (knowledge). The function of competitive (rival) similarity (FRiS) is proposed as a similarity measure for classification and pattern recognition applications. This function allows one to design effective algorithms for solving all basic data mining tasks, obtain quantitative estimates of the compactness of patterns and the informativeness of feature spaces, and construct easily interpretable decision rules. The method is suitable for any number of patterns regardless of the nature of their distributions and conditionality of training samples (the ratio of the numbers of objects and features). The usefulness of the FRiS is shown by solving a problems of molecular biology.

  5. Extension of trigonometric and hyperbolic functions to vectorial arguments and its application to the representation of rotations and Lorentz transformations

    NASA Astrophysics Data System (ADS)

    Yamasaki, H.

    1983-11-01

    The use of the axial vector representing a three-dimensional rotation makes the rotation representation much more compact by extending the trigonometric functions to vectorial arguments. Similarly, the pure Lorentz transformations are compactly treated by generalizing a scalar rapidity to a vector quantity in spatial three-dimensional cases and extending hyperbolic functions to vectorial arguments. A calculation of the Wigner rotation simplified by using the extended functions illustrates the fact that the rapidity vector space obeys hyperbolic geometry. New representations bring a Lorentz-invariant fundamental equation of motion corresponding to the Galilei-invariant equation of Newtonian mechanics.

  6. Existence of hyperbolic calorons

    PubMed Central

    Sibner, Lesley; Sibner, Robert; Yang, Yisong

    2015-01-01

    Recent work of Harland shows that the SO(3)-symmetric, dimensionally reduced, charge-N self-dual Yang–Mills calorons on the hyperbolic space H3×S1 may be obtained through constructing N-vortex solutions of an Abelian Higgs model as in the study of Witten on multiple instantons. In this paper, we establish the existence of such minimal action charge-N calorons by constructing arbitrarily prescribed N-vortex solutions of the Witten type equations.

  7. An approach to the development of numerical algorithms for first order linear hyperbolic systems in multiple space dimensions: The constant coefficient case

    NASA Technical Reports Server (NTRS)

    Goodrich, John W.

    1995-01-01

    Two methods for developing high order single step explicit algorithms on symmetric stencils with data on only one time level are presented. Examples are given for the convection and linearized Euler equations with up to the eighth order accuracy in both space and time in one space dimension, and up to the sixth in two space dimensions. The method of characteristics is generalized to nondiagonalizable hyperbolic systems by using exact local polynominal solutions of the system, and the resulting exact propagator methods automatically incorporate the correct multidimensional wave propagation dynamics. Multivariate Taylor or Cauchy-Kowaleskaya expansions are also used to develop algorithms. Both of these methods can be applied to obtain algorithms of arbitrarily high order for hyperbolic systems in multiple space dimensions. Cross derivatives are included in the local approximations used to develop the algorithms in this paper in order to obtain high order accuracy, and improved isotropy and stability. Efficiency in meeting global error bounds is an important criterion for evaluating algorithms, and the higher order algorithms are shown to be up to several orders of magnitude more efficient even though they are more complex. Stable high order boundary conditions for the linearized Euler equations are developed in one space dimension, and demonstrated in two space dimensions.

  8. An ODE for boundary layer separation on a sphere and a hyperbolic space

    NASA Astrophysics Data System (ADS)

    Chan, Chi Hin; Czubak, Magdalena; Yoneda, Tsuyoshi

    2014-07-01

    Ma and Wang derived an equation linking the separation location and times for the boundary layer separation of incompressible fluid flows. The equation gave a necessary condition for the separation (bifurcation) point. The purpose of this paper is to generalize the equation to other geometries, and to phrase it as a simple ODE. Moreover we consider the Navie-Stokes equation with the Coriolis effect, which is related to the presence of trade winds on Earth. A ∂-singular point (bifurcation point) occurs at t0 iff a function α1(t) satisfies α1(t0)=0. The above result is a generalization of [10] which is considered in the Euclidean space R2. We can regard α1(t), α2(t) and α3(t) as a part of the inflow profile. However η(t) is not. Let us be more precise. Choose p˜∈∂K close to p0∈∂K, and let K˜≔{p∈M-K:d(p,p˜)0. It is reasonable to assume uθ does not grow polynomially for the r direction (this is due to the observation of the "boundary layer", since the flow should be a uniform one away from the boundary). Thus, it should be reasonable to focus on the following two cases: (Poiseuille type profile) -k2α1(t)+2kα2(t)<0 (α1(t)>0, α2(t)<0) and α3(t) is small comparing with α1(t) and α2(t). (Before separation profile) 2kα2(t)+α3(t)<0 (α2(t)>0, α3(t)<0) and α1(t) is small comparing with α2(t) and α3(t). In this point of view, the well-known physical phenomena of "adverse

  9. MIRIS: A Compact Wide-field Infrared Space Telescope

    NASA Astrophysics Data System (ADS)

    Han, Wonyong; Lee, Dae-Hee; Jeong, Woong-Seob; Park, Youngsik; Moon, Bongkon; Park, Sung-Joon; Pyo, Jeonghyun; Kim, Il-Joong; Park, Won-Kee; Lee, Dukhang; Seon, Kwang-Il; Nam, Uk-Won; Cha, Sang-Mok; Park, Kwijong; Park, Jang-Hyun; Yuk, In-Soo; Ree, Chang Hee; Jin, Ho; Choel Yang, Sun; Park, Hong-Young; Shin, Goo-Hwan; Seo, Joung-Ki; Rhee, Seung-Wu; Park, Jong-Oh; Lee, Hyung Mok; Murakami, Hiroshi; Matsumoto, Toshio

    2014-09-01

    A compact infrared space telescope called MIRIS (Multi-purpose Infra-Red Imaging System) was developed by the Korea Astronomy and Space Science Institute (KASI), and launched onboard the Science and Technology Satellite-3 of Korea (STSAT-3) in 2013 November. The main mission of MIRIS is the Paschen-α emission line survey along the Galactic plane and the cosmic infrared background (CIB) observation, particularly around the north ecliptic pole region. For these missions, a wide field of view (3.67 × 3.67°) with an angular resolution of 51.6'' and wavelength coverage from 0.9 ~ 2.0 μm have been adopted for MIRIS, having optical components consisting of a 80 mm main lens and four other lenses with F/2 focal ratio optics. The opto-mechanical system was carefully designed to minimize any effects from shock during the launch process and thermal variation. Also, the telescope was designed to use a passive cooling technique to maintain the temperature around 200 K in order to reduce thermal noise. A micro Stirling cooler was used to cool down the Teledyne PICNIC infrared array to 90 K, which was equipped in a dewar with four filters for infrared passbands of I, H, and Paschen-α and a dual-band continuum line filter. MIRIS system was integrated into the STSAT-3 as its primary payload and successfully passed required tests in the laboratory, such as thermal-vacuum, vibration, and shock tests. MIRIS is now operating in sun synchronous orbits for initial tests and has observed its first images successfully.

  10. The Post-Winternitz system on spherical and hyperbolic spaces: A proof of the superintegrability making use of complex functions and a curvature-dependent formalism

    NASA Astrophysics Data System (ADS)

    Rañada, Manuel F.

    2015-10-01

    Two important advances in integrability have been the recent discovery of the higher-order superintegrability of the Tremblay-Turbiner-Winternitz system (related to the harmonic oscillator) and the Post-Winternitz system (related to the Kepler problem). The properties of the TTW system have been recently studied on the two-dimensional spherical Sκ2 (κ > 0) and hyperbolic Hκ2 (κ < 0) spaces by making use of a curvature-dependent formalism and the existence of a complex factorization for the higher-order constant of motion. Now in this Letter we prove that a similar technique can also be applied for the study of the PW system.

  11. Hyperbolic interfaces.

    PubMed

    Giomi, Luca

    2012-09-28

    Fluid interfaces, such as soap films, liquid droplets, or lipid membranes, are known to give rise to several special geometries, whose complexity and beauty continue to fascinate us, as observers of the natural world, and challenge us as scientists. Here I show that a special class of surfaces of constant negative Gaussian curvature can be obtained in fluid interfaces equipped with an orientational ordered phase. These arise in various soft and biological materials, such as nematic liquid crystals, cytoskeletal assemblies, or hexatic colloidal suspensions. The purely hyperbolic morphology originates from the competition between surface tension, that reduces the area of the interface at the expense of increasing its Gaussian curvature, and the orientational elasticity of the ordered phase, that in turn suffers for the distortion induced by the underlying curvature. PMID:23030106

  12. Hyperbolic Interfaces

    NASA Astrophysics Data System (ADS)

    Giomi, Luca

    2012-09-01

    Fluid interfaces, such as soap films, liquid droplets, or lipid membranes, are known to give rise to several special geometries, whose complexity and beauty continue to fascinate us, as observers of the natural world, and challenge us as scientists. Here I show that a special class of surfaces of constant negative Gaussian curvature can be obtained in fluid interfaces equipped with an orientational ordered phase. These arise in various soft and biological materials, such as nematic liquid crystals, cytoskeletal assemblies, or hexatic colloidal suspensions. The purely hyperbolic morphology originates from the competition between surface tension, that reduces the area of the interface at the expense of increasing its Gaussian curvature, and the orientational elasticity of the ordered phase, that in turn suffers for the distortion induced by the underlying curvature.

  13. Non-uniformly hyperbolic flows and shadowing

    NASA Astrophysics Data System (ADS)

    Sun, Wenxiang; Tian, Xueting; Vargas, Edson

    2016-07-01

    We consider a hyperbolic ergodic measure of a C1 flow on a compact manifold. Under the hypothesis that there are no fixed points and that the Oseledec splitting of the normal bundle satisfies a limit domination property, we prove that the measure has a shadowing property. As an application of this result we prove that the measure can be approached on the weak* topology by measures supported on hyperbolic periodic orbits.

  14. A formula for the first eigenvalue of the Dirac operator on compact spin symmetric spaces

    SciTech Connect

    Milhorat, Jean-Louis

    2006-04-15

    Let G/K be a simply connected spin compact inner irreducible symmetric space, endowed with the metric induced by the Killing form of G sign-changed. We give a formula for the square of the first eigenvalue of the Dirac operator in terms of a root system of G. As an example of application, we give the list of the first eigenvalues for the spin compact irreducible symmetric spaces endowed with a quaternion-Kaehler structure.

  15. Criteria for compactness in L{sup p}-spaces, p {>=} 0

    SciTech Connect

    Krotov, Veniamin G

    2012-07-31

    The paper puts forward new compactness criteria for spaces of summable and measurable functions on a metric space with measure satisfying the doubling condition. These criteria are formulated in terms of either local smoothness inequalities or maximal operators that measure local smoothness. Bibliography: 28 titles.

  16. The Hyperbolic Sine Cardinal and the Catenary

    ERIC Educational Resources Information Center

    Sanchez-Reyes, Javier

    2012-01-01

    The hyperbolic function sinh(x)/x receives scant attention in the literature. We show that it admits a clear geometric interpretation as the ratio between length and chord of a symmetric catenary segment. The inverse, together with the use of dimensionless parameters, furnishes a compact, explicit construction of a general catenary segment of…

  17. A Compact Remote Heat Transfer Device for Space Cryocoolers

    NASA Astrophysics Data System (ADS)

    Yan, T.; Zhao, Y.; Liang, T.

    In this paper a compact remote heat transfer device (CRHD) for cryocoolers is proposed. This device is especially attractive in cases where cryocoolers are not easy to set near the heat source, generally the infrared sensor. The CRHD is designed on basis of the concept of loop heat pipes, while the primary evaporator is located near the cryocooler cold head and a simple tube-in-tube secondary evaporator is remotely located and thermally connected with the heat source for cooling. With such a device a cooling power of 1 W is achieved across a heat transfer distance of about 2 m. The major problem of this device is the low heat transfer efficiency (1 W of net cooling power at the cost of about 7 W of cooling power from the cryocooler), and in the future a secondary wicked evaporator will be used instead of the tube-in-tube evaporator in order to improve the efficiency.

  18. All-metal, compact heat exchanger for space cryocoolers

    NASA Technical Reports Server (NTRS)

    Swift, Walter L.; Valenzuela, Javier; Sixsmith, Herbert

    1990-01-01

    This report describes the development of a high performance, all metal compact heat exchanger. The device is designed for use in a reverse Brayton cryogenic cooler which provides five watts of refrigeration at 70 K. The heat exchanger consists of a stainless steel tube concentrically assembled within a second stainless steel tube. Approximately 300 pairs of slotted copper disks and matching annular slotted copper plates are positioned along the centerline axis of the concentric tubes. Each of the disks and plates has approximately 1200 precise slots machined by means of a special electric discharge process. Positioning of the disk and plate pairs is accomplished by means of dimples in the surface of the tubes. Mechanical and thermal connections between the tubes and plate/disk pairs are made by solder joints. The heat exchanger assembly is 9 cm in diameter by 50 cm in length and has a mass of 10 kg. The predicted thermal effectiveness is greater than 0.985 at design conditions. Pressure loss at design conditions is less than 5 kPa in both fluid passages. Tests were performed on a subassembly of plates integrally soldered to two end headers. The measured thermal effectiveness of the test article exceeded predicted levels. Pressure losses were negligibly higher than predictions.

  19. Hyperbolic graph generator

    NASA Astrophysics Data System (ADS)

    Aldecoa, Rodrigo; Orsini, Chiara; Krioukov, Dmitri

    2015-11-01

    Networks representing many complex systems in nature and society share some common structural properties like heterogeneous degree distributions and strong clustering. Recent research on network geometry has shown that those real networks can be adequately modeled as random geometric graphs in hyperbolic spaces. In this paper, we present a computer program to generate such graphs. Besides real-world-like networks, the program can generate random graphs from other well-known graph ensembles, such as the soft configuration model, random geometric graphs on a circle, or Erdős-Rényi random graphs. The simulations show a good match between the expected values of different network structural properties and the corresponding empirical values measured in generated graphs, confirming the accurate behavior of the program.

  20. Compact IR laser for calibration of space based sensors

    SciTech Connect

    Kietrick, K.M.; Dezenberg, G.; Hamilton, C.; Vann, J.; LaSala, J.

    1996-04-17

    An Er:YAG laser, operating at 2.94 microns, has been developed for in-theater calibration of space based infrared sensors. The laser is used to illuminate a spaceborne sensor focal plane from a surveyed ground reference point. The known reference point is compared to the laser position reported by the sensor, and boresight corrections are made. The Er:YAG laser is side pumped by a InGaAs diode array and is tuned to an atmospheric microwindow with and intracavity etalon. This technology is being directly applied to meet Army requirements for enhanced deep strike targeting information supplied to theater weapons systems.

  1. Compact Microwave Mercury Ion Clock for Space Applications

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Tu, Meirong; Chung, Sang K.; MacNeal, Paul

    2007-01-01

    We review progress in developing a small Hg ion clock for space operation based on breadboard ion-clock physics package where Hg ions are shuttled between a quadrupole and a 16-pole rf trap. With this architecture we have demonstrated short-term stability approx.1-2x10(exp -13) at 1 second, averaging to 10-15 at 1 day. This development shows that H-maser quality stabilities can be produced in a small clock package, comparable in size to an ultra-stable quartz oscillator required or holding 1-2x10(exp -13) at 1 second. We have completed an ion clock physics package designed to withstand vibration of launch and are currently building a approx. 1 kg engineering model for test. We also discuss frequency steering software algorithms that simultaneously measure ion signal size and lamp light output, useful for long term operation and self-optimization of microwave power and return engineering data.

  2. A Compact Nuclear Fusion Reactor for Space Flights

    NASA Astrophysics Data System (ADS)

    Nastoyashchiy, Anatoly F.

    2006-05-01

    A small-scale nuclear fusion reactor is suggested based on the concepts of plasma confinement (with a high pressure gas) which have been patented by the author. The reactor considered can be used as a power setup in space flights. Among the advantages of this reactor is the use of a D3He fuel mixture which at burning gives main reactor products — charged particles. The energy balance considerably improves, as synchrotron radiation turn out "captured" in the plasma volume, and dangerous, in the case of classical magnetic confinement, instabilities in the direct current magnetic field configuration proposed do not exist. As a result, the reactor sizes are quite suitable (of the order of several meters). A possibility of making reactive thrust due to employment of ejection of multiply charged ions formed at injection of pellets from some adequate substance into the hot plasma center is considered.

  3. Reliable compact electrical power source systems for space launch vehicles

    SciTech Connect

    Young, A.R.

    1996-12-31

    Described herein are several key technologies utilized in the design of a family of direct-drive turboalternator systems for space launch vehicles. These systems automatically provide conditioned and regulated electrical power at various voltages, powering actuators, valves, and avionics throughout the vehicle. The simple and robust ring-wound two-pole toothless alternator operates at peripheral speeds, making it suitable to be driven directly by a turbine, thereby eliminating the weight, reliability, zero ``g`` lubrication, and cooling issues of a speed-reducing gearbox, while allowing the turbine to operate at reasonable efficiency. Additionally, the use of self-aligning foil bearing and catalytic combustors or cold gas propellants enhance the reliability. The power conditioner and electronic controller provide hands-off regulated ac or dc power on demand, maintaining critical parameters within established limits and performance while reporting on built-in health-monitoring tests.

  4. The Thermal Infrared Compact Imaging Spectrometer (TIRCIS): a follow-on to the Space Ultra Compact Hyperspectral Imager (SUCHI)

    NASA Astrophysics Data System (ADS)

    Crites, S. T.; Wright, R.; Lucey, P. G.; Chan, J.; Gabrieli, A.; Garbeil, H.; Horton, K. A.; Imai-Hong, A. K. R.; Pilger, E. J.; Wood, M.; Yoneshige, L.

    2015-05-01

    The Thermal Infrared Compact Imaging Spectrometer (TIRCIS) is a long wave infrared (LWIR, 8-14 microns) hyperspectral imager designed as the follow-on to the University of Hawaii's SUCHI (Space Ultra Compact Hyperspectral Imager). SUCHI is a low-mass (<9kg), low-volume (10x12x40cm3) LWIR spectrometer designed as the primary payload on the University of Hawaii-built 'HiakaSat' microsatellite. SUCHI is based on a variable-gap Fabry Perot interferometer employed as a Fourier transform spectrometer with images collected by a commercial off-the-shelf microbolometer contained inside a 1-atm sealed vessel. The sensor has been fully integrated with the HiakaSat microsatellite and is awaiting launch in 2015. The TIRCIS instrument is based on the same principles but takes lessons learned from SUCHI and applies them to a new design with improvements in spatial resolution, spectral resolution and spectral responsivity. The TIRCIS instrument is based on an uncooled microbolometer array with custom detector coatings to enhance responsivity towards 7 microns. Like SUCHI, TIRCIS utilizes a variable-gap Fabry Perot interferometer to create the spectra, but three different interferometer wedges with varying slopes resulting in spectral resolution ranging from 44 cm-1 to 6.5 cm-1 will be tested to explore tradeoffs between spectral resolution and sensitivity. TIRCIS is designed to achieve 120 m spatial resolution, compared with 230 m for SUCHI, from a theoretical 500 km orbit. It will be used for ground and aircraft data collection but will undergo environmental testing to demonstrate its relevance to the space environment. TIRCIS has been fully designed and is entering fabrication, with an operational instrument to be delivered in October, 2015.

  5. Discretizing singular point sources in hyperbolic wave propagation problems

    NASA Astrophysics Data System (ADS)

    Petersson, N. Anders; O'Reilly, Ossian; Sjögreen, Björn; Bydlon, Samuel

    2016-09-01

    We develop high order accurate source discretizations for hyperbolic wave propagation problems in first order formulation that are discretized by finite difference schemes. By studying the Fourier series expansions of the source discretization and the finite difference operator, we derive sufficient conditions for achieving design accuracy in the numerical solution. Only half of the conditions in Fourier space can be satisfied through moment conditions on the source discretization, and we develop smoothness conditions for satisfying the remaining accuracy conditions. The resulting source discretization has compact support in physical space, and is spread over as many grid points as the number of moment and smoothness conditions. In numerical experiments we demonstrate high order of accuracy in the numerical solution of the 1-D advection equation (both in the interior and near a boundary), the 3-D elastic wave equation, and the 3-D linearized Euler equations.

  6. Movable-molybdenum-reflector reactivity experiments for control studies of compact space power reactor concepts

    NASA Technical Reports Server (NTRS)

    Fox, T. A.

    1973-01-01

    An experimental reflector reactivity study was made with a compact cylindrical reactor using a uranyl fluoride - water fuel solution. The reactor was axially unreflected and radially reflected with segments of molybdenum. The reflector segments were displaced incrementally in both the axial and radial dimensions, and the shutdown of each configuration was measured by using the pulsed-neutron source technique. The reactivity effects for axial and radial displacement of reflector segments are tabulated separately and compared. The experiments provide data for control-system studies of compact-space-power-reactor concepts.

  7. Hyperbolic Hopfield neural networks.

    PubMed

    Kobayashi, M

    2013-02-01

    In recent years, several neural networks using Clifford algebra have been studied. Clifford algebra is also called geometric algebra. Complex-valued Hopfield neural networks (CHNNs) are the most popular neural networks using Clifford algebra. The aim of this brief is to construct hyperbolic HNNs (HHNNs) as an analog of CHNNs. Hyperbolic algebra is a Clifford algebra based on Lorentzian geometry. In this brief, a hyperbolic neuron is defined in a manner analogous to a phasor neuron, which is a typical complex-valued neuron model. HHNNs share common concepts with CHNNs, such as the angle and energy. However, HHNNs and CHNNs are different in several aspects. The states of hyperbolic neurons do not form a circle, and, therefore, the start and end states are not identical. In the quantized version, unlike complex-valued neurons, hyperbolic neurons have an infinite number of states. PMID:24808287

  8. Modelling of the void space of tablets compacted over a range of pressures.

    PubMed

    Ridgway, C J; Ridgway, K; Matthews, G P

    1997-04-01

    A previously developed computer model, named Pore-Cor, has been used to simulate the changes in the void-space dimensions which occur during the compaction of tablets over a range of pressures. The tablets were made by mixing pharmaceutical grade crystalline lactose and an anti-inflammatory compound in the proportion 4:1. Compacts were made by placing a weighed amount of the mixed powder into a stainless-steel die and applying pressure with a hand-operated calibrated hydraulic press. Compacts were prepared at eight pressures over the hydraulic pressure range 1 to 8 ton in-2 (15.4-123.2 MPa) in 1 ton in-2 increments. Mercury-intrusion curves were measured for the eight samples by use of a porosimeter and the Pore-Cor package was then used to simulate the mercury-intrusion curves and generate void-space models of the correct porosity. The experimental and simulated characteristic throat diameter, the experimental and simulated porosity, and the simulated permeability of the tablets have all been shown to follow expected trends. The successful modelling of void-structure parameters, which are difficult or impossible to measure experimentally, opens the way to an improved understanding of the strength of compacts. PMID:9232534

  9. Representation of the contextual statistical model by hyperbolic amplitudes

    SciTech Connect

    Khrennikov, Andrei

    2005-06-01

    We continue the development of a so-called contextual statistical model (here context has the meaning of a complex of physical conditions). It is shown that, besides contexts producing the conventional trigonometric cos-interference, there exist contexts producing the hyperbolic cos-interference. Starting with the corresponding interference formula of total probability we represent such contexts by hyperbolic probabilistic amplitudes or in the abstract formalism by normalized vectors of a hyperbolic analogue of the Hilbert space. There is obtained a hyperbolic Born's rule. Incompatible observables are represented by noncommutative operators. This paper can be considered as the first step towards hyperbolic quantum probability. We also discuss possibilities of experimental verification of hyperbolic quantum mechanics: in physics of elementary particles, string theory as well as in experiments with nonphysical systems, e.g., in psychology, cognitive sciences, and economy.

  10. Boundary control problems for quasilinear systems of hyperbolic equations

    NASA Astrophysics Data System (ADS)

    Alekseenko, A. E.; Kholodov, A. S.; Kholodov, Ya. A.

    2016-06-01

    For quasilinear systems of hyperbolic equations, the nonclassical boundary value problem of controlling solutions with the help of boundary conditions is considered. Previously, this problem was extensively studied in the case of the simplest hyperbolic equations, namely, the scalar wave equation and certain linear systems. The corresponding problem formulations and numerical solution algorithms are extended to nonlinear (quasilinear and conservative) systems of hyperbolic equations. Some numerical (grid-characteristic) methods are considered that were previously used to solve the above problems. They include explicit and implicit conservative difference schemes on compact stencils that are linearizations of Godunov's method. The numerical algorithms and methods are tested as applied to well-known linear examples.

  11. Fourth order difference methods for hyperbolic IBVP's

    NASA Technical Reports Server (NTRS)

    Gustafsson, Bertil; Olsson, Pelle

    1994-01-01

    Fourth order difference approximations of initial-boundary value problems for hyperbolic partial differential equations are considered. We use the method of lines approach with both explicit and compact implicit difference operators in space. The explicit operator satisfies an energy estimate leading to strict stability. For the implicit operator we develop boundary conditions and give a complete proof of strong stability using the Laplace transform technique. We also present numerical experiments for the linear advection equation and Burgers' equation with discontinuities in the solution or in its derivative. The first equation is used for modeling contact discontinuities in fluid dynamics, the second one for modeling shocks and rarefaction waves. The time discretization is done with a third order Runge-Kutta TVD method. For solutions with discontinuities in the solution itself we add a filter based on second order viscosity. In case of the non-linear Burger's equation we use a flux splitting technique that results in an energy estimate for certain different approximations, in which case also an entropy condition is fulfilled. In particular we shall demonstrate that the unsplit conservative form produces a non-physical shock instead of the physically correct rarefaction wave. In the numerical experiments we compare our fourth order methods with a standard second order one and with a third order TVD-method. The results show that the fourth order methods are the only ones that give good results for all the considered test problems.

  12. Hyperbolic Triangle Centers

    NASA Astrophysics Data System (ADS)

    Ungar, A. A.

    Einstein's addition law of three-dimensional relativistically admissible velocities is the corner stone of Einstein's three-vector formalism of the special theory of relativity that he founded in 1905. In this chapter, we present Einstein addition along with its role in nonassociative algebra and hyperbolic geometry. We make no demands upon readers of this book as to a prior acquaintance with either special relativity, nonassociative algebra or hyperbolic geometry.

  13. Compact Low Cost Hybrid DC/DC Converter Controller For Space Applications

    NASA Astrophysics Data System (ADS)

    Volpi, Gian Franco; Contissa, Alessandro; Mantegazza, Massimiliano

    2011-10-01

    The need for low cost, space qualified (ESA requirements), compact DC/DC converters is becoming increasingly important both for commercial market and programs controlled by space administration. Market is also showing request for large scale production. To face market needs, the design of low power multi- output DC/DC converters can be based on small and low mass hybrid controllers for better mechanical optimization. Moreover, this approach, maintaining robust performances against harsh space environment, allows taking the advantages typical of recurrent design: high reliability and reduction of cost. Also, using the hybrid controller allows designers to focus just on power transformer and filters, reducing the time necessary to complete the design. This paper shall provide description of the standard Thales Alenia Space hybrid controller in its two variants: 40V-760V (HYLPSC03RAD) and 20.5V-43V (HYLPSC04RAD) bus voltage.

  14. Classification of hyperbolic Dynkin diagrams, root lengths and Weyl group orbits

    NASA Astrophysics Data System (ADS)

    Carbone, Lisa; Chung, Sjuvon; Cobbs, Leigh; McRae, Robert; Nandi, Debajyoti; Naqvi, Yusra; Penta, Diego

    2010-04-01

    We give a criterion for a Dynkin diagram, equivalently a generalized Cartan matrix, to be symmetrizable. This criterion is easily checked on the Dynkin diagram. We obtain a simple proof that the maximal rank of a Dynkin diagram of compact hyperbolic type is 5, while the maximal rank of a symmetrizable Dynkin diagram of compact hyperbolic type is 4. Building on earlier classification results of Kac, Kobayashi-Morita, Li and Saçlio\\skew3\\tildeg lu, we present the 238 hyperbolic Dynkin diagrams in ranks 3-10, 142 of which are symmetrizable. For each symmetrizable hyperbolic generalized Cartan matrix, we give a symmetrization and hence the distinct lengths of real roots in the corresponding root system. For each such hyperbolic root system we determine the disjoint orbits of the action of the Weyl group on real roots. It follows that the maximal number of disjoint Weyl group orbits on real roots in a hyperbolic root system is 4.

  15. Compact time- and space-integrating SAR processor: design and development status

    NASA Astrophysics Data System (ADS)

    Haney, Michael W.; Levy, James J.; Christensen, Marc P.; Michael, Robert R., Jr.; Mock, Michael M.

    1994-06-01

    Progress toward a flight demonstration of the acousto-optic time- and space- integrating real-time SAR image formation processor program is reported. The concept overcomes the size and power consumption limitations of electronic approaches by using compact, rugged, and low-power analog optical signal processing techniques for the most computationally taxing portions of the SAR imaging problem. Flexibility and performance are maintained by the use of digital electronics for the critical low-complexity filter generation and output image processing functions. The results reported include tests of a laboratory version of the concept, a description of the compact optical design that will be implemented, and an overview of the electronic interface and controller modules of the flight-test system.

  16. The design and fabrication of a prototype trash compacting unit. [for long duration space missions

    NASA Technical Reports Server (NTRS)

    1973-01-01

    A prototype trash compactor, that is compatible with the anticipated requirements of future long-term space missions, is described. Preliminary problem definition studies were conducted to identify typical types and quantities of waste materials to be expected from a typical mission. Bench-scale compaction tests were then conducted on typical waste materials to determine force/compaction curves. These data were used to design a boilerplate compactor that was fabricated to prove the feasibility of the basic design concept. A final design was then prepared from which the deliverable unit was fabricated. Design concepts are presented for suggested further development of the compactor, including a version that is capable of handling wet biodegradable wastes.

  17. Hidden symmetry of hyperbolic monopole motion

    NASA Astrophysics Data System (ADS)

    Gibbons, G. W.; Warnick, C. M.

    2007-10-01

    Hyperbolic monopole motion is studied for well separated monopoles. It is shown that the motion of a hyperbolic monopole in the presence of one or more fixed monopoles is equivalent to geodesic motion on a particular submanifold of the full moduli space. The metric on this submanifold is found to be a generalisation of the multi-centre Taub-NUT metric introduced by LeBrun. The one centre case is analysed in detail as a special case of a class of systems admitting a conserved Runge-Lenz vector. The two centre problem is also considered. An integrable classical string motion is exhibited.

  18. Some compactness tests in Banach spaces by Cesaro means of Fourier coefficients

    NASA Astrophysics Data System (ADS)

    Öztürk, Seda

    2015-09-01

    Let H be a complex Banach space, T be the topological group of the unit circle with respect to the Euclidean topology, α be a strongly continuous isometric linear representation of T in H, {Fkα}k ∈ℤ be the family of Fourier coefficients with respect to α, and {σkα}k ∈ℤ be Cesaro means of the family {Fkα}k ∈ℤ . In this work, we give some compactness tests for closed subsets of H.

  19. QED{sub 3} on a space-time lattice: Compact versus noncompact formulation

    SciTech Connect

    Fiore, R.; Giudice, P.; Giuliano, D.; Marmottini, D.; Papa, A.; Sodano, P.

    2005-11-01

    We study quantum electrodynamics in a (2+1)-dimensional space-time with two flavors of dynamical fermions by numerical simulations on the lattice. We discretize the theory using both the compact and the noncompact formulations and analyze the behavior of the chiral condensate and of the monopole density in the finite lattice regime as well as in the continuum limit. By comparing the results obtained with the two approaches, we draw some conclusions about the possible equivalence of the two lattice formulations in the continuum limit.

  20. Metric properties in the mean of polynomials on compact isotropy irreducible homogeneous spaces

    NASA Astrophysics Data System (ADS)

    Gichev, V. M.

    2013-06-01

    Let M=G/H be a compact connected isotropy irreducible Riemannian homogeneous manifold, where G is a compact Lie group (may be, disconnected) acting on M by isometries. This class includes all compact irreducible Riemannian symmetric spaces and, for example, the tori {R }^n/{Z }^n with the natural action on itself extended by the finite group generated by all permutations of the coordinates and inversions in circle factors. We say that u is a polynomial on M if it belongs to some G-invariant finite dimensional subspace {E } of L^2(M). We compute or estimate from above the averages over the unit sphere {S } in {E } for some metric quantities such as Hausdorff measures of level set and norms in L^p(M), 1le ple infty , where M is equipped with the invariant probability measure. For example, the averages over {S } of Vert uVert _{L^p(M)}, pge 2, are less than sqrt{p+1/e} independently of M and {E }.

  1. Braneworld localisation in hyperbolic spacetime

    NASA Astrophysics Data System (ADS)

    Crampton, B.; Pope, C. N.; Stelle, K. S.

    2014-12-01

    We present a construction employing a type IIA supergravity and 3-form flux background together with an NS5-brane that localises massless gravity near the 5-brane worldvolume. The nonsingular underlying type IIA solution is a lift to 10D of the vacuum solution of the 6D Salam-Sezgin model and has a hyperbolic structure in the lifting dimensions. A fully back-reacted solution including the NS5-brane is constructed by recognising the 10D Salam-Sezgin vacuum solution as a "brane resolved through transgression." The background hyperbolic structure plays a key rôle in generating a mass gap in the spectrum of the transverse-space wave operator, which gives rise to the localisation of gravity on the 6D NS5-brane worldvolume, or, equally, in a further compactification to 4D. Also key to the successful localisation of gravity is the specific form of the corresponding transverse wavefunction Schrödinger problem, which asymptotically involves a V = -1 /(4 ρ 2) potential, where ρ is the transverse-space radius, and for which the NS5-brane source gives rise to a specific choice of self-adjoint extension for the transverse wave operator. The corresponding boundary condition as ρ → 0 ensures the masslessness of gravity in the effective braneworld theory. Above the mass gap, there is a continuum of massive states which give rise to small corrections to Newton's law.

  2. Compact-sized and broadband carpet cloak and free-space cloak.

    PubMed

    Ma, Hui Feng; Jiang, Wei Xiang; Yang, Xin Mi; Zhou, Xiao Yang; Cui, Tie Jun

    2009-10-26

    Recently, invisible cloaks have attracted much attention due to their exciting property of invisibility, which are based on a solid theory of transformation optics and quasi-conformal mapping. Two kinds of cloaks have been proposed: free-space cloaks, which can render objects in free space invisible to incident radiation, and carpet cloaks (or ground-plane cloaks), which can hide objects under the conducting ground. The first free-space and carpet cloaks were realized in the microwave frequencies using metamaterials. The free-space cloak was composed of resonant metamaterials, and hence had restriction of narrow bandwidth and high loss; the carpet cloak was made of non-resonant metamaterials, which have broad bandwidth and low loss. However, the carpet cloak has a severe restriction of large size compared to the cloaked object. The above restrictions become the bottlenecks to the real applications of free-space and carpet cloaks. Here we report the first experimental demonstration of broadband and low-loss directive free-space cloak and compact-sized carpet cloak based on a recent theoretical study. Both cloaks are realized using non-resonant metamaterials in the microwave frequency, and good invisibility properties have been observed in experiments. This approach represents a major step towards the real applications of invisibility cloaks. PMID:19997219

  3. Study and Developement of Compact Permanent Magnet Hall Thrusters for Future Brazillian Space Missions

    NASA Astrophysics Data System (ADS)

    Ferreira, Jose Leonardo; Martins, Alexandre; Cerda, Rodrigo

    2016-07-01

    The Plasma Physics Laboratory of UnB has been developing a Permanent Magnet Hall Thruster (PHALL) for the UNIESPAÇO program, part of the Space Activities Program conducted by AEB- The Brazillian Space Agency since 2004. Electric propulsion is now a very successful method for primary and secondary propulsion systems. It is essential for several existing geostationary satellite station keeping systems and for deep space long duration solar system missions, where the thrusting system can be designed to be used on orbit transfer maneuvering and/or for satellite attitude control in long term space missions. Applications of compact versions of Permanent Magnet Hall Thrusters on future brazillian space missions are needed and foreseen for the coming years beginning with the use of small divergent cusp field (DCFH) Hall Thrusters type on CUBESATS ( 5-10 kg , 1W-5 W power consumption) and on Micro satellites ( 50- 100 kg, 10W-100W). Brazillian (AEB) and German (DLR) space agencies and research institutions are developing a new rocket dedicated to small satellite launching. The VLM- Microsatellite Launch Vehicle. The development of PHALL compact versions can also be important for the recently proposed SBG system, a future brazillian geostationary satellite system that is already been developed by an international consortium of brazillian and foreign space industries. The exploration of small bodies in the Solar System with spacecraft has been done by several countries with increasing frequency in these past twenty five years. Since their historical beginning on the sixties, most of the Solar System missions were based on gravity assisted trajectories very much depended on planet orbit positioning relative to the Sun and the Earth. The consequence was always the narrowing of the mission launch window. Today, the need for Solar System icy bodies in situ exploration requires less dependence on gravity assisted maneuvering and new high precision low thrust navigation methods

  4. Efficiently enclosing the compact binary parameter space by singular-value decomposition

    SciTech Connect

    Cannon, Kipp; Hanna, Chad; Keppel, Drew

    2011-10-15

    Gravitational-wave searches for the merger of compact binaries use matched filtering as the method of detecting signals and estimating parameters. Such searches construct a fine mesh of filters covering a signal parameter space at high density. Previously it has been shown that singular-value decomposition can reduce the effective number of filters required to search the data. Here we study how the basis provided by the singular-value decomposition changes dimension as a function of template-bank density. We will demonstrate that it is sufficient to use the basis provided by the singular-value decomposition of a low-density bank to accurately reconstruct arbitrary points within the boundaries of the template bank. Since this technique is purely numerical, it may have applications to interpolating the space of numerical relativity waveforms.

  5. Development of a Compact, Efficient Cooling Pump for Space Suit Life Support Systems

    NASA Technical Reports Server (NTRS)

    van Boeyen, Roger; Reeh, Jonathan; Trevino, Luis

    2009-01-01

    A compact, low-power electrochemically-driven fluid cooling pump is currently being developed by Lynntech, Inc. With no electric motor and minimal lightweight components, the pump is significantly lighter than conventional rotodynamic and displacement pumps. Reliability and robustness is achieved with the absence of rotating or moving components (apart from the bellows). By employing sulfonated polystyrene-based proton exchange membranes, rather than conventional Nafion membranes, a significant reduction in the actuator power consumption was demonstrated. Lynntech also demonstrated that these membranes possess the necessary mechanical strength, durability, and temperature range for long life space operation. The preliminary design for a Phase II prototype pump compares very favorably to the fluid cooling pumps currently used in space suit primary life support systems (PLSSs). Characteristics of the electrochemically-driven pump are described and the benefits of the technology as a replacement for electric motor pumps in mechanically pumped single-phase fluid loops is discussed.

  6. Spectral properties of the Ruelle operator on the Walters class over compact spaces

    NASA Astrophysics Data System (ADS)

    Cioletti, Leandro; Silva, Eduardo A.

    2016-08-01

    Recently the Ruelle–Perron–Frobenius theorem was proved for Hölder potentials defined on the symbolic space Ω ={{M}{N}} , where (the alphabet) M is any compact metric space. In this paper, we extend this theorem to the Walters space W(Ω ) , in similar general alphabets. We also describe in detail an abstract procedure to obtain the Fréchet analyticity of the Ruelle operator under quite general conditions and we apply this result to prove the analytic dependence of this operator on both Walters and Hölder spaces. The analyticity of the pressure functional on Hölder spaces is established. An exponential decay of the correlations is shown when the Ruelle operator has the spectral gap property. A new (and natural) family of Walters potentials (on a finite alphabet derived from the Ising model) which do not have an exponential decay of the correlations is presented. Because of the lack of exponential decay, for such potentials there is an absence of the spectral gap for the Ruelle operator. The key idea in proving the lack of exponential decay of the correlations is the Griffiths–Kelly–Sherman inequalities.

  7. Angular spectrum method with compact space-bandwidth: generalization and full-field accuracy.

    PubMed

    Kozacki, Tomasz; Falaggis, Konstantinos

    2016-07-01

    A recent Letter [Opt. Lett.40, 3420 (2015)OPLEDP0146-959210.1364/OL.40.003420] reported a modified angular spectrum method that uses a sampling scheme based on a compact space-bandwidth product representation. That technique is useful for focusing and defocusing propagation cases and is generalized here for the case of propagation between two defocus planes. The proposed method employs paraxial spherical phase factors and modified propagation kernels to reduce the size of the numerical space-bandwidth product needed for wave field calculations. A Wigner distribution analysis is carried out in order to ensure high accuracy of the calculations in the entire computational domain. This is achieved by analyzing the evolution of the generalized space-bandwidth product when passing through the propagation algorithm for various space-frequency constraints. The results allow the derivations of sampling criteria, and, despite this, also show that a small amount of space/frequency zero padding significantly extends the capability of the recently reported modified angular spectrum method. Simulations validate the high accuracy of that method and verify a computational and memory gain of more than two orders of magnitude when comparing this technique with the conventional angular spectrum method. PMID:27409185

  8. Compact Tissue-equivalent Proportional Counter for Deep Space Human Missions

    PubMed Central

    Straume, T.; Braby, L.A.; Borak, T.B.; Lusby, T.; Warner, D.W.; Perez-Nunez, D.

    2015-01-01

    Abstract Effects on human health from the complex radiation environment in deep space have not been measured and can only be simulated here on Earth using experimental systems and beams of radiations produced by accelerators, usually one beam at a time. This makes it particularly important to develop instruments that can be used on deep-space missions to measure quantities that are known to be relatable to the biological effectiveness of space radiation. Tissue-equivalent proportional counters (TEPCs) are such instruments. Unfortunately, present TEPCs are too large and power intensive to be used beyond low Earth orbit (LEO). Here, the authors describe a prototype of a compact TEPC designed for deep space applications with the capability to detect both ambient galactic cosmic rays and intense solar particle event radiation. The device employs an approach that permits real-time determination of (and thus quality factor) using a single detector. This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate. Tests with γ rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h−1. Measurements of for 200 MeV n−1 carbon ions were better than 10%. Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%. PMID:26313585

  9. A New Discretization Method of Order Four for the Numerical Solution of One-Space Dimensional Second-Order Quasi-Linear Hyperbolic Equation

    ERIC Educational Resources Information Center

    Mohanty, R. K.; Arora, Urvashi

    2002-01-01

    Three level-implicit finite difference methods of order four are discussed for the numerical solution of the mildly quasi-linear second-order hyperbolic equation A(x, t, u)u[subscript xx] + 2B(x, t, u)u[subscript xt] + C(x, t, u)u[subscript tt] = f(x, t, u, u[subscript x], u[subscript t]), 0 less than x less than 1, t greater than 0 subject to…

  10. Hyperbolic polaritons in nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Zhiyuan; Rubio, Angel; Guinea, Francisco; Basov, Dimitri; Fogler, Michael

    2015-03-01

    Hyperbolic optical materials (HM) are characterized by permittivity tensor that has both positive and negative principal values. Collective electromagnetic modes (polaritons) of HM have novel properties promising for various applications including subdiffractional imaging and on-chip optical communication. Hyperbolic response is actively investigated in the context of metamaterials, anisotropic polar insulators, and layered superconductors. We study polaritons in spheroidal HM nanoparticles using Hamiltonian optics. The field equations are mapped to classical dynamics of fictitious particles (wave packets) of an indefinite Hamiltonian. This dynamics is quantized using the Einstein-Brillouin-Keller quantization rule. The eigenmodes are classified as either bulk or surface according to whether their transverse momenta are real or imaginary. To model how such hyperbolic polaritons can be probed by near-field experiments, we compute the field distribution induced inside and outside the spheroid by an external point dipole. At certain magic frequencies the field shows striking geometric patterns whose origin is traced to the classical periodic orbits. The theory is applied to natural hyperbolic materials hexagonal boron nitride and superconducting LaSrCuO.

  11. Hyperbolic octonion formulation of the fluid Maxwell equations

    NASA Astrophysics Data System (ADS)

    Demir, Süleyman; Tanişli, Murat

    2016-03-01

    The equations of compressible ideal fluids analogous to those of electromagnetism are reformulated in terms of hyperbolic octonions. Furthermore, the wave equations with source terms are generalized in a compact and elegant form. The analogy between fluid mechanics and electromagnetism is also argued by considering the previous octonionic formulations in relevant literature.

  12. A compact time-resolved system for near infrared spectroscopy based on wavelength space multiplexing

    NASA Astrophysics Data System (ADS)

    Re, Rebecca; Contini, Davide; Caffini, Matteo; Cubeddu, Rinaldo; Spinelli, Lorenzo; Torricelli, Alessandro

    2010-11-01

    We designed and developed a compact dual-wavelength and dual-channel time-resolved system for near-infrared spectroscopy studies of muscle and brain. The system employs pulsed diode lasers as sources, compact photomultipliers, and time-correlated single photon counting boards for detection. To exploit the full temporal and dynamic range of the acquisition technique, we implemented an approach based on wavelength space multiplexing: laser pulses at the two wavelengths are alternatively injected into the two channels by means of an optical 2×2 switch. In each detection line (i.e., in each temporal window), the distribution of photon time-of-flights at one wavelength is acquired. The proposed approach increases the signal-to-noise ratio and avoids wavelength cross-talk with respect to the typical approach based on time multiplexing. The instrument was characterized on tissue phantoms to assess its properties in terms of linearity, stability, noise, and reproducibility. Finally, it was successfully tested in preliminary in vivo measurements on muscle during standard cuff occlusion and on the brain during a motor cortex response due to hand movements.

  13. Hubble space telescope observations and geometric models of compact multipolar planetary nebulae

    SciTech Connect

    Hsia, Chih-Hao; Chau, Wayne; Zhang, Yong; Kwok, Sun E-mail: wwlljj1314@gmail.com E-mail: sunkwok@hku.hk

    2014-05-20

    We report high angular resolution Hubble Space Telescope observations of 10 compact planetary nebulae (PNs). Many interesting internal structures, including multipolar lobes, arcs, two-dimensional rings, tori, and halos, are revealed for the first time. These results suggest that multipolar structures are common among PNs, and these structures develop early in their evolution. From three-dimensional geometric models, we have determined the intrinsic dimensions of the lobes. Assuming the lobes are the result of interactions between later-developed fast winds and previously ejected asymptotic giant branch winds, the geometric structures of these PNs suggest that there are multiple phases of fast winds separated by temporal variations and/or directional changes. A scenario of evolution from lobe-dominated to cavity-dominated stages is presented. The results reported here will provide serious constraints on any dynamical models of PNs.

  14. Multiscale quantum propagation using compact-support wavelets in space and time

    SciTech Connect

    Wang Haixiang; Acevedo, Ramiro; Molle, Heather; Mackey, Jeffrey L.; Kinsey, James L.; Johnson, Bruce R.

    2004-10-22

    Orthogonal compact-support Daubechies wavelets are employed as bases for both space and time variables in the solution of the time-dependent Schroedinger equation. Initial value conditions are enforced using special early-time wavelets analogous to edge wavelets used in boundary-value problems. It is shown that the quantum equations may be solved directly and accurately in the discrete wavelet representation, an important finding for the eventual goal of highly adaptive multiresolution Schroedinger equation solvers. While the temporal part of the basis is not sharp in either time or frequency, the Chebyshev method used for pure time-domain propagations is adapted to use in the mixed domain and is able to take advantage of Hamiltonian matrix sparseness. The orthogonal separation into different time scales is determined theoretically to persist throughout the evolution and is demonstrated numerically in a partially adaptive treatment of scattering from an asymmetric Eckart barrier.

  15. Covariant hyperbolization of force-free electrodynamics

    NASA Astrophysics Data System (ADS)

    Carrasco, F. L.; Reula, O. A.

    2016-04-01

    Force-free electrodynamics (FFE) is a nonlinear system of equations modeling the evolution of the electromagnetic field, in the presence of a magnetically dominated relativistic plasma. This configuration arises on several astrophysical scenarios which represent exciting laboratories to understand physics in extreme regimes. We show that this system, when restricted to the correct constraint submanifold, is symmetric hyperbolic. In numerical applications, it is not feasible to keep the system in that submanifold, and so it is necessary to analyze its structure first in the tangent space of that submanifold and then in a whole neighborhood of it. As has been shown [1], a direct (or naive) formulation of this system (in the whole tangent space) results in a weakly hyperbolic system of evolution equations for which well-posedness for the initial value formulation does not follow. Using the generalized symmetric hyperbolic formalism of Geroch [2], we introduce here a covariant hyperbolization for the FFE system. In fact, in analogy to the usual Maxwell case, a complete family of hyperbolizers is found, both for the restricted system on the constraint submanifold as well as for a suitably extended system defined in a whole neighborhood of it. A particular symmetrizer among the family is then used to write down the pertaining evolution equations, in a generic (3 +1 ) decomposition on a background spacetime. Interestingly, it turns out that for a particular choice of the lapse and shift functions of the foliation, our symmetrized system reduces to the one found in [1]. Finally, we analyze the characteristic structure of the resulting evolution system.

  16. Compact Tissue-equivalent Proportional Counter for Deep Space Human Missions.

    PubMed

    Straume, T; Braby, L A; Borak, T B; Lusby, T; Warner, D W; Perez-Nunez, D

    2015-10-01

    Effects on human health from the complex radiation environment in deep space have not been measured and can only be simulated here on Earth using experimental systems and beams of radiations produced by accelerators, usually one beam at a time. This makes it particularly important to develop instruments that can be used on deep-space missions to measure quantities that are known to be relatable to the biological effectiveness of space radiation. Tissue-equivalent proportional counters (TEPCs) are such instruments. Unfortunately, present TEPCs are too large and power intensive to be used beyond low Earth orbit (LEO). Here, the authors describe a prototype of a compact TEPC designed for deep space applications with the capability to detect both ambient galactic cosmic rays and intense solar particle event radiation. The device employs an approach that permits real-time determination of yD (and thus quality factor) using a single detector. This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate. Tests with g rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h(-1). Measurements of yD for 200 MeV n(-1) carbon ions were better than 10%. Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%. PMID:26313585

  17. Violation of hyperbolicity in a diffusive medium with local hyperbolic attractor

    NASA Astrophysics Data System (ADS)

    Kuptsov, Pavel V.; Kuznetsov, Sergey P.

    2009-07-01

    Departing from a system of two nonautonomous amplitude equations, demonstrating hyperbolic chaotic dynamics, we construct a one-dimensional medium as an ensemble of such local elements introducing spatial coupling via diffusion. When length of the medium is small, all spatial cells oscillate synchronously, reproducing the local hyperbolic dynamics. This regime is characterized by a single positive Lyapunov exponent. The hyperbolicity survives when the system gets larger in length so that the second Lyapunov exponent passes zero and the oscillations become inhomogeneous in space. However, at a point where the third Lyapunov exponent becomes positive, some bifurcation occur that results in violation of the hyperbolicity due to the emergence of one-dimensional intersections of contracting and expanding tangent subspaces along trajectories on the attractor. Further growth of the length results in the two-dimensional intersections of expanding and contracting subspaces that we classify as a stronger type of the violation. Beyond the point of the hyperbolicity loss, the system demonstrates an extensive spatiotemporal chaos typical for extended chaotic systems: when the length of the system increases the Kaplan-Yorke dimension, the number of positive Lyapunov exponents and the upper estimate for Kolmogorov-Sinai entropy grow linearly, while the Lyapunov spectrum tends to a limiting curve.

  18. Hyperbole, abstract motion and spatial knowledge: sequential versus simultaneous scanning.

    PubMed

    Catricalà, Maria; Guidi, Annarita

    2012-08-01

    Hyperbole is an interesting trope in the perspective of Space Grammar, since it is related to the displacing of a limit (Lausberg in Elemente der literarischen Rhetorik. M.H. Verlag, Munchen 1967; see the Ancient Greek meaning 'to throw over' > 'exaggerate'). Hyperbole semantic mechanisms are related to virtual scanning (Holmqvist and Płuciennik in Imagery in language. Peter Lang, Frankfurt am Main, pp 777-785, 2004). Basic concepts of SIZE and QUANTITY, related image-schemas (IS) and conceptual metaphors (UP IS MORE; IMPORTANT IS BIG: Lakoff 1987, Johnson 1987) are implied in hyperbole processing. The virtual scanning is the simulation of a perceptual domain (here, the vertically oriented space). The virtual limit is defined by expected values on the relevant scale. Since hyperbole is a form of intensification, its linguistic interest lies in cases involving the extremes of a scale, for which a limit can be determined (Schemann 1994). In this experimental study, we analyze the concept of 'limit' in terms of 'abstract motion' and 'oriented space' domains (Langacker 1990) with respect to hyperboles expressed by Italian Verbs of movement. The IS considered are PATH and SOURCE-PATH-GOAL. The latter corresponds to a virtual scale whose limit is arrived at, or overcome, in hyperboles. PMID:22820865

  19. Continued Development of Compact Multi-gas Monitor for Life Support Systems Control in Space

    NASA Technical Reports Server (NTRS)

    Delgado-Alonso, Jesús; Phillips, Straun; Chullen, Cinda; Quinn, Gregory

    2016-01-01

    Miniature optic gas sensors (MOGS) based on luminescent materials have shown great potential as alternatives to Near-Infrared-based gas sensor systems for the advanced space suit portable life support system (PLSS). The unique capability of MOGS for carbon dioxide and oxygen monitoring under wet conditions has been reported, as has the fast recovery of MOGS humidity sensors after long periods of being wet. Lower volume and power requirements are also potential advantages of MOGS over both traditional and advanced Non-Dispersive Infrared (NDIR) gas sensors, which have shown so far longer life than luminescent sensors. This paper presents the most recent results in the development and analytical validation of a compact multi-gas sensor unit based on luminescent sensors for the PLSS. Results of extensive testing are presented, including studies conducted at Intelligent Optical Systems laboratories, a United Technology Corporation Aerospace Systems (UTAS) laboratory, and a Johnson Space Center laboratory. The potential of this sensor technology for gas monitoring in PLSSs and other life support systems and the advantages and limitations found through detailed sensor validation are discussed.

  20. SUSEE: A Compact, Lightweight Space Nuclear Power System Using Present Water Reactor Technology

    NASA Astrophysics Data System (ADS)

    Maise, George; Powell, James; Paniagua, John

    2006-01-01

    The SUSEE space reactor system uses existing nuclear fuels and the standard steam cycle to generate electrical and thermal power for a wide range of in-space and surface applications, including manned bases, sub-surface mobile probes to explore thick ice deposits on Mars and the Jovian moons, and mobile rovers. SUSEE cycle efficiency, thermal to electric, ranges from ~20 to 24%, depending on operating parameters. Rejection of waste heat is by a lightweight condensing radiator that can be launched as a compact rolled-up package and deployed into flat panels when appropriate. The 50 centimeter diameter SUSEE reactor can provide power over the range of 10 kW(e) to 1 MW(e) for a period of 10 years. Higher power outputs are possible using slightly larger reactors. System specific weight (reactor, turbine, generator, piping, and radiator is ~3 kg/kW(e). Two SUSEE reactor options are described, based on the existing Zr/O2 cermet and the UH3/ZrH2 TRIGA nuclear fuels.

  1. SUSEE: A Compact, Lightweight Space Nuclear Power System Using Present Water Reactor Technology

    SciTech Connect

    Maise, George; Powell, James; Paniagua, John

    2006-01-20

    The SUSEE space reactor system uses existing nuclear fuels and the standard steam cycle to generate electrical and thermal power for a wide range of in-space and surface applications, including manned bases, sub-surface mobile probes to explore thick ice deposits on Mars and the Jovian moons, and mobile rovers. SUSEE cycle efficiency, thermal to electric, ranges from {approx}20 to 24%, depending on operating parameters. Rejection of waste heat is by a lightweight condensing radiator that can be launched as a compact rolled-up package and deployed into flat panels when appropriate. The 50 centimeter diameter SUSEE reactor can provide power over the range of 10 kW(e) to 1 MW(e) for a period of 10 years. Higher power outputs are possible using slightly larger reactors. System specific weight (reactor, turbine, generator, piping, and radiator) is {approx}3 kg/kW(e). Two SUSEE reactor options are described, based on the existing Zr/O2 cermet and the UH3/ZrH2 TRIGA nuclear fuels.

  2. Hyperbolic resonances of metasurface cavities.

    PubMed

    Keene, D; Durach, M

    2015-07-13

    We propose a new class of optical resonator structures featuring one or two metasurface reflectors or metacavities and predict that such resonators support novel hyperbolic resonances. As an example of such resonances we introduce hyperbolic Tamm plasmons (HTPs) and hyperbolic Fabry-Perot resonances (HFPs). The hyperbolic optical modes feature low-loss incident power re-distribution over TM and TE polarization output channels, clover-leaf anisotropic dispersion, and other unique properties which are tunable and are useful for multiple applications. PMID:26191916

  3. Optimal space of linear classical observables for Maxwell k-forms via spacelike and timelike compact de Rham cohomologies

    NASA Astrophysics Data System (ADS)

    Benini, Marco

    2016-05-01

    Being motivated by open questions in gauge field theories, we consider non-standard de Rham cohomology groups for timelike compact and spacelike compact support systems. These cohomology groups are shown to be isomorphic respectively to the usual de Rham cohomology of a spacelike Cauchy surface and its counterpart with compact support. Furthermore, an analog of the usual Poincaré duality for de Rham cohomology is shown to hold for the case with non-standard supports as well. We apply these results to find optimal spaces of linear observables for analogs of arbitrary degree k of both the vector potential and the Faraday tensor. The term optimal has to be intended in the following sense: The spaces of linear observables we consider distinguish between different configurations; in addition to that, there are no redundant observables. This last point in particular heavily relies on the analog of Poincaré duality for the new cohomology groups.

  4. Single-Mode, High Repetition Rate, Compact Ho:YLF Laser for Space-Borne Lidar Applications

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Wong, Teh-Hwa; Chen, Songsheng; Petros, Mulugeta; Singh, Upendra N.

    2014-01-01

    A single transverse/longitudinal mode, compact Q-switched Ho:YLF laser has been designed and demonstrated for space-borne lidar applications. The pulse energy is between 34-40 mJ for 100-200 Hz operation. The corresponding peak power is >1 MW.

  5. Study and Developement of Compact Permanent Magnet Hall Thrusters for Future Brazillian Space Missions

    NASA Astrophysics Data System (ADS)

    Ferreira, Jose Leonardo; Martins, Alexandre; Cerda, Rodrigo

    2016-07-01

    The Plasma Physics Laboratory of UnB has been developing a Permanent Magnet Hall Thruster (PHALL) for the UNIESPAÇO program, part of the Space Activities Program conducted by AEB- The Brazillian Space Agency since 2004. Electric propulsion is now a very successful method for primary and secondary propulsion systems. It is essential for several existing geostationary satellite station keeping systems and for deep space long duration solar system missions, where the thrusting system can be designed to be used on orbit transfer maneuvering and/or for satellite attitude control in long term space missions. Applications of compact versions of Permanent Magnet Hall Thrusters on future brazillian space missions are needed and foreseen for the coming years beginning with the use of small divergent cusp field (DCFH) Hall Thrusters type on CUBESATS ( 5-10 kg , 1W-5 W power consumption) and on Micro satellites ( 50- 100 kg, 10W-100W). Brazillian (AEB) and German (DLR) space agencies and research institutions are developing a new rocket dedicated to small satellite launching. The VLM- Microsatellite Launch Vehicle. The development of PHALL compact versions can also be important for the recently proposed SBG system, a future brazillian geostationary satellite system that is already been developed by an international consortium of brazillian and foreign space industries. The exploration of small bodies in the Solar System with spacecraft has been done by several countries with increasing frequency in these past twenty five years. Since their historical beginning on the sixties, most of the Solar System missions were based on gravity assisted trajectories very much depended on planet orbit positioning relative to the Sun and the Earth. The consequence was always the narrowing of the mission launch window. Today, the need for Solar System icy bodies in situ exploration requires less dependence on gravity assisted maneuvering and new high precision low thrust navigation methods

  6. Hyperbolicity measures democracy in real-world networks.

    PubMed

    Borassi, Michele; Chessa, Alessandro; Caldarelli, Guido

    2015-09-01

    In this work, we analyze the hyperbolicity of real-world networks, a geometric quantity that measures if a space is negatively curved. We provide two improvements in our understanding of this quantity: first of all, in our interpretation, a hyperbolic network is "aristocratic", since few elements "connect" the system, while a non-hyperbolic network has a more "democratic" structure with a larger number of crucial elements. The second contribution is the introduction of the average hyperbolicity of the neighbors of a given node. Through this definition, we outline an "influence area" for the vertices in the graph. We show that in real networks the influence area of the highest degree vertex is small in what we define "local" networks (i.e., social or peer-to-peer networks), and large in "global" networks (i.e., power grid, metabolic networks, or autonomous system networks). PMID:26465533

  7. Hyperbolicity measures democracy in real-world networks

    NASA Astrophysics Data System (ADS)

    Borassi, Michele; Chessa, Alessandro; Caldarelli, Guido

    2015-09-01

    In this work, we analyze the hyperbolicity of real-world networks, a geometric quantity that measures if a space is negatively curved. We provide two improvements in our understanding of this quantity: first of all, in our interpretation, a hyperbolic network is "aristocratic", since few elements "connect" the system, while a non-hyperbolic network has a more "democratic" structure with a larger number of crucial elements. The second contribution is the introduction of the average hyperbolicity of the neighbors of a given node. Through this definition, we outline an "influence area" for the vertices in the graph. We show that in real networks the influence area of the highest degree vertex is small in what we define "local" networks (i.e., social or peer-to-peer networks), and large in "global" networks (i.e., power grid, metabolic networks, or autonomous system networks).

  8. The Hype over Hyperbolic Browsers.

    ERIC Educational Resources Information Center

    Allen, Maryellen Mott

    2002-01-01

    Considers complaints about the usability in the human-computer interaction aspect of information retrieval and discusses information visualization, the Online Library of Information Visualization Environments, hyperbolic information structure, subject searching, real-world applications, relational databases and hyperbolic trees, and the future of…

  9. A Compact and Robust Method for Spectropolarimetry: Application to Space Exploration

    NASA Astrophysics Data System (ADS)

    Sparks, W. B.

    2012-12-01

    A compact and robust method for spectropolarimetry is described which lends itself, in principle, to application in the field and in space. With space-based polarimetry, profoundly important astronomical topics may be addressed, including the search for extrasolar planets, their characterization and the presence of life. Within the Solar System, exploration and characterization opportunities are greatly enhanced. Polarization observations provide fundamental and unique insights into planetary characteristics, and may be invaluable in establishing the presence and nature of extrasolar planets. Within the Solar System, time resolved spectropolarimetry may probe aerosol, surface, plasma and atmospheric scattering processes, and cometary and zodiacal dust and dusty ring systems. Beyond the Solar System, in the search for extrasolar planets seen by reflected light, polarization can play a critical role in the recognition of planets, the characterization of their environment, and of the planets themselves. We may identify Rayleigh scattering atmospheres, liquid oceans, clouds, rocks and ices from their polarimetric signatures. A powerful new dimension is introduced by the addition of circular polarization. Through the homochirality of biological molecules, circular polarization may offer one of the purest biosignatures available. Homochirality arises as a consequence of self-replication hence is likely to be generic to all forms of biological life. We have shown that a variety of photosynthetic microbial organisms and macroscopic vegetation, yield distinctive signatures in their circular polarization spectra, hence circular polarization may prove to be an effective way to remotely sense photosynthesis. These topics are best tackled from space; a planetary probe or a space-based telescope. However, there are serious challenges to precision polarimetry in space, some applicable to polarimetry in general, which include: fragile components such as photoelastic modulators or

  10. Possibility of hyperbolic tunneling

    SciTech Connect

    Lobo, Francisco S. N.; Mimoso, Jose P.

    2010-08-15

    Traversable wormholes are primarily useful as 'gedanken experiments' and as a theoretician's probe of the foundations of general relativity. In this work, we analyze the possibility of having tunnels in a hyperbolic spacetime. We obtain exact solutions of static and pseudo-spherically symmetric spacetime tunnels by adding exotic matter to a vacuum solution referred to as a degenerate solution of class A. The physical properties and characteristics of these intriguing solutions are explored, and through the mathematics of embedding it is shown that particular constraints are placed on the shape function, that differ significantly from the Morris-Thorne wormhole. In particular, it is shown that the energy density is always negative, and the radial pressure is positive, at the throat, contrary to the Morris-Thorne counterpart. Specific solutions are also presented by considering several equations of state, and by imposing restricted choices for the shape function or the redshift function.

  11. Hyperbolic mapping of complex networks based on community information

    NASA Astrophysics Data System (ADS)

    Wang, Zuxi; Li, Qingguang; Jin, Fengdong; Xiong, Wei; Wu, Yao

    2016-08-01

    To improve the hyperbolic mapping methods both in terms of accuracy and running time, a novel mapping method called Community and Hyperbolic Mapping (CHM) is proposed based on community information in this paper. Firstly, an index called Community Intimacy (CI) is presented to measure the adjacency relationship between the communities, based on which a community ordering algorithm is introduced. According to the proposed Community-Sector hypothesis, which supposes that most nodes of one community gather in a same sector in hyperbolic space, CHM maps the ordered communities into hyperbolic space, and then the angular coordinates of nodes are randomly initialized within the sector that they belong to. Therefore, all the network nodes are so far mapped to hyperbolic space, and then the initialized angular coordinates can be optimized by employing the information of all nodes, which can greatly improve the algorithm precision. By applying the proposed dual-layer angle sampling method in the optimization procedure, CHM reduces the time complexity to O(n2) . The experiments show that our algorithm outperforms the state-of-the-art methods.

  12. Criteria of cyclic compactness of the sets from Lp - spaces, associated with vector measure

    NASA Astrophysics Data System (ADS)

    Chilin, V.; Rakhimov, B.; Rakhimov, A.

    2013-09-01

    We study the conditional expectations in the Lp-modules associated with a partition of unity of a Boolean algebra. Cyclic compactness criteria of the subsets of Lp found in terms of convergent nets of conditional expectations.

  13. Blackbody Theory for Hyperbolic Materials

    NASA Astrophysics Data System (ADS)

    Biehs, Svend-Age; Lang, Slawa; Petrov, Alexander Yu.; Eich, Manfred; Ben-Abdallah, Philippe

    2015-10-01

    The blackbody theory is revisited in the case of thermal electromagnetic fields inside uniaxial anisotropic media in thermal equilibrium with a heat bath. When these media are hyperbolic, we show that the spectral energy density of these fields radically differs from that predicted by Planck's blackbody theory and that the maximum of the spectral energy density determined by Wien's law is redshifted. Finally, we derive the Stefan-Boltzmann law for hyperbolic media which becomes a quadratic function of the heat bath temperature.

  14. Compact free-space optical terminal for multi-gigabit signal transmissions with a single-mode fiber

    NASA Astrophysics Data System (ADS)

    Arimoto, Yoshinori

    2009-02-01

    This paper shows the design and the performance of a new free-space optical communication terminal including the results of the indoor and outdoor demonstration experiments in a short link distance. To provide flexible and high-speed connectivity to the terrestrial free-space optical communications, a new compact laser communication terminal has been developed at NICT. The terminal has a feature to connect the free-space laser beam directly to single mode fiber by using a special fiber coupler to focus the free-space laser beam and couple it into the single mode fiber, fast and accurate fine tracking system and a small refractive-type telescope with diffraction limited performance. The bandwidth of the fine tracking system is more than 5 kHz using an off-the-shelf miniature Galvano mirror actuator and an analog PID controller.

  15. Broadband absorption engineering of hyperbolic metafilm patterns

    NASA Astrophysics Data System (ADS)

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-03-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting.

  16. Broadband absorption engineering of hyperbolic metafilm patterns.

    PubMed

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-01-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting. PMID:24675706

  17. Broadband absorption engineering of hyperbolic metafilm patterns

    PubMed Central

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-01-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting. PMID:24675706

  18. Computational methods for estimation of parameters in hyperbolic systems

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Ito, K.; Murphy, K. A.

    1983-01-01

    Approximation techniques for estimating spatially varying coefficients and unknown boundary parameters in second order hyperbolic systems are discussed. Methods for state approximation (cubic splines, tau-Legendre) and approximation of function space parameters (interpolatory splines) are outlined and numerical findings for use of the resulting schemes in model "one dimensional seismic inversion' problems are summarized.

  19. Hawking into Unruh mapping for embeddings of hyperbolic type

    NASA Astrophysics Data System (ADS)

    Paston, S. A.

    2015-07-01

    We study the conditions of the existence of Hawking into Unruh mapping for hyperbolic (Fronsdal-type) metric embeddings into the Minkowski space, for which timelines are hyperbolas. Many examples are known for global embeddings into the Minkowskian spacetime (GEMS), with such mapping for physically interesting metrics with some symmetry. However, examples of embeddings, both smooth and hyperbolic, for which there is no mapping, were also given. In the present work we prove that Hawking into Unruh mapping takes place for a hyperbolic embedding of an arbitrary metric with a time-like Killing vector and a Killing horizon if the embedding of such type exists and smoothly covers the horizon. At the same time, we do not assume any symmetry (spherical, for example), except the time translational invariance, which corresponds to the existence of a time-like Killing vector. We show that the known examples of the absence of mapping do not satisfy the formulated conditions of its existence.

  20. Characteristics of trapped magnetic fields in HTS bulk annuli with various axial spaces for compact NMR magnets

    NASA Astrophysics Data System (ADS)

    Kim, S. B.; Imai, M.; Takano, R.; Kashima, K.; Hahn, S.

    2010-11-01

    Recently, the performance of high-temperature superconducting (HTS) bulks such as a critical current density, size, and mechanical strength has been improved. In consequence, various applications with HTS bulks such as motors, bearings, and flywheels are being investigated by many research groups; Compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of an HTS bulk more than 11.7 T, 500 MHz 1H NMR frequency, has been developed. This new compact NMR magnet out of HTS bulks is far less expensive than those conventional NMR magnets and expected to be widely used in food and drug industry. In design and manufacture of those compact NMR magnets, the issues of spatial homogeneity and temporal stability of trapped magnetic fields in HTS bulk annuli are very important. In this paper, the characteristics of the trapped magnetic fields in a stack of assembled HTS bulk annuli were investigated with various axial spaces between HTS bulks, experimentally and analytically.

  1. Optics near a hyperbolic defect

    NASA Astrophysics Data System (ADS)

    Fumeron, Sébastien; Berche, Bertrand; Santos, Fernando; Pereira, Erms; Moraes, Fernando

    2015-12-01

    We examine the properties of a family of defects called hyperbolic disclinations, and discuss their possible use for the design of perfect optical absorbers. In hyperbolic metamaterials, the ratio of ordinary and extraordinary permittivities is negative, which leads to an effective metric of Kleinian signature (two timelike coordinates). Considering a disclination in the hyperbolic nematic host matrix, we show that the timelike geodesics are Poinsot spirals, i.e., whatever the impact parameter of an incident light beam, it is confined and whirls about the defect core. The trapping effect does not require light to be coherent. This property also remains in the wave formalism, which may be the sign for many potential applications.

  2. Blackbody Theory for Hyperbolic Materials.

    PubMed

    Biehs, Svend-Age; Lang, Slawa; Petrov, Alexander Yu; Eich, Manfred; Ben-Abdallah, Philippe

    2015-10-23

    The blackbody theory is revisited in the case of thermal electromagnetic fields inside uniaxial anisotropic media in thermal equilibrium with a heat bath. When these media are hyperbolic, we show that the spectral energy density of these fields radically differs from that predicted by Planck's blackbody theory and that the maximum of the spectral energy density determined by Wien's law is redshifted. Finally, we derive the Stefan-Boltzmann law for hyperbolic media which becomes a quadratic function of the heat bath temperature. PMID:26551116

  3. Sharp estimates of the Kobayashi metric and Gromov hyperbolicity

    NASA Astrophysics Data System (ADS)

    Bertrand, Florian

    2008-09-01

    Let D={[rho]<0} be a smooth relatively compact domain in a four-dimensional almost complex manifold (M,J), where [rho] is a J-plurisubharmonic function on a neighborhood of and strictly J-plurisubharmonic on a neighborhood of [not partial differential]D. We give sharp estimates of the Kobayashi metric. Our approach is based on an asymptotic quantitative description of both the domain D and the almost complex structure J near a boundary point. Following Z.M. Balogh and M. Bonk [Z.M. Balogh, M. Bonk, Gromov hyperbolicity and the Kobayashi metric on strictly pseudoconvex domains, Comment. Math. Helv. 75 (2000) 504-533], these sharp estimates provide the Gromov hyperbolicity of the domain D.

  4. Double-pass Cassegrain revisited: a compact optic for space missions

    NASA Astrophysics Data System (ADS)

    Beach, David A.

    2000-10-01

    If intended to operate outside the Earth's atmosphere, the imaging optics demanded of a designer become critical. A typical specification would be diffraction-limited imaging over a usefully wide field angle with a broad spectral bandpass, high transmittance, no distortion and no vignetting. When combined with demands for a light and compact structure, such a specification calls for some trade-offs if a real system is to be devised. This paper describes an exceptionally compact imaging system in which the only significant trade-off is the 21% transmittance loss caused by the central obstruction of a Cassegrain-like optic. The entire 1° field angle is diffraction limited for all pupil diameters up to 1m (which would give 0.2 arcsec resolution), while providing a flat, distortionless, unvignetted, f/2.4 image, bandpass-limited only by the reflective coatings of the totally catoptric design. For fields less than 1 degree(s), scaling is possible to very large pupil diameters while maintaining full-field diffraction-limited imaging. By employing a single-axis, double-pass, four-reflection format, compactness is such that the overall length is less than the pupil diameter. The primary and tertiary mirror surfaces are formed from a single substrate. The primary, secondary and tertiary mirrors are hyperboloids of increasing eccentricity, and the quaternary is a weak aspheric zonal corrector. The geometry is such that stray light exclusion is simply achieved without occluding the optical path. The rearward propagating final beam provides significant useful free surrounding volume for cryostat structures, filters and shutters. A further example is given of a scalable f/1.25 version of the system.

  5. Euclidean, Spherical, and Hyperbolic Shadows

    ERIC Educational Resources Information Center

    Hoban, Ryan

    2013-01-01

    Many classical problems in elementary calculus use Euclidean geometry. This article takes such a problem and solves it in hyperbolic and in spherical geometry instead. The solution requires only the ability to compute distances and intersections of points in these geometries. The dramatically different results we obtain illustrate the effect…

  6. Visible-frequency hyperbolic metasurface

    NASA Astrophysics Data System (ADS)

    High, Alexander A.; Devlin, Robert C.; Dibos, Alan; Polking, Mark; Wild, Dominik S.; Perczel, Janos; de Leon, Nathalie P.; Lukin, Mikhail D.; Park, Hongkun

    2015-06-01

    Metamaterials are artificial optical media composed of sub-wavelength metallic and dielectric building blocks that feature optical phenomena not present in naturally occurring materials. Although they can serve as the basis for unique optical devices that mould the flow of light in unconventional ways, three-dimensional metamaterials suffer from extreme propagation losses. Two-dimensional metamaterials (metasurfaces) such as hyperbolic metasurfaces for propagating surface plasmon polaritons have the potential to alleviate this problem. Because the surface plasmon polaritons are guided at a metal-dielectric interface (rather than passing through metallic components), these hyperbolic metasurfaces have been predicted to suffer much lower propagation loss while still exhibiting optical phenomena akin to those in three-dimensional metamaterials. Moreover, because of their planar nature, these devices enable the construction of integrated metamaterial circuits as well as easy coupling with other optoelectronic elements. Here we report the experimental realization of a visible-frequency hyperbolic metasurface using single-crystal silver nanostructures defined by lithographic and etching techniques. The resulting devices display the characteristic properties of metamaterials, such as negative refraction and diffraction-free propagation, with device performance greatly exceeding those of previous demonstrations. Moreover, hyperbolic metasurfaces exhibit strong, dispersion-dependent spin-orbit coupling, enabling polarization- and wavelength-dependent routeing of surface plasmon polaritons and two-dimensional chiral optical components. These results open the door to realizing integrated optical meta-circuits, with wide-ranging applications in areas from imaging and sensing to quantum optics and quantum information science.

  7. Deep Hubble Space Telescope imaging of a compact radio galaxy at z = 2.390

    NASA Technical Reports Server (NTRS)

    Windhorst, Rogier; Mathis, Douglas F.; Keel, William C.

    1992-01-01

    The radio galaxy with the highest redshift in the Leiden-Berkeley Deep Survey, 53W002, is described and examined in terms of UV profile in relation to an early-type galaxy. The HST WFC images have a resolution of 0.2 arcsec FWHM, and the I- and V-band structures are assessed. The source is elongated in a manner similar to the Ly alpha cloud in V, and the structure is highly compact in I. The present object with a young starburst has very high central UV surface brightnesses relative to nearby luminous early-type galaxies, while the light profiles are similar. The data are concluded to suggest that 53W002 is a young galaxy that has a regular light profile at z = 2.390 even though it has been forming stars since not more than about 0.5 Gyr before z = 2.390. Such a scenario is consistent with concurrent dynamical collapse and star formation in the compact radio galaxy.

  8. Vascular Spaces in Compact Bone: A Technique to Correct a Common Misinterpretation of Structure

    ERIC Educational Resources Information Center

    Locke, M.; Dean, Rob L.

    2003-01-01

    Old bones are often discolored by the grime that infiltrates spaces in the matrix once occupied by blood vessels. This suggested that allowing dry bone to absorb colorants might be a useful way to show the three dimensional complexity of bone vascularization. The authors have developed a simple way to show blood vessels spaces in bone at a glance…

  9. Reducing compaction effort and incorporating air permeability in Proctor testing for design of urban green spaces on cohesive soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is well established that compaction negatively affects agronomic productivity, that air permeability is a sensitive measure of the degree of soil compaction and therefore a good indicator of soil productivity impairment from compaction. Cohesive soils in urban settings are often heavily compacted...

  10. Effect of blade spacing of polycrystalline diamond compact (PDC) bits on stability of drillstrings

    SciTech Connect

    Elsayed, M.A.; Dupuy, C.A.

    1997-07-01

    The geometry of PDC bits, particularly their blade spacing, plays a major role in stability of the drillstrings to which they are attached. In this paper, the authors use a bit model in which the cutters are arrayed in radial blades and examine the effect of blade spacing on stability. They show that for a given bit size, blade spacing may be changed to produce stable cutting in a desired speed range. This data, combined with downhole assembly design, may be used to optimize operating conditions for drillstrings.

  11. A Compact Disk Type Plasma Propulsion System with Modulated Magnetic Field for Nanoscale Space Vehicles

    NASA Astrophysics Data System (ADS)

    Fukuda, Takeshi; Ueda, Satoshi; Ohnishi, Yukihiro; Inomoto, Michiaki

    2008-12-01

    A compact 5 mm disk type plasma thruster simply composed of only a set of antenna windings and bias field coil which produces significant thrust of 0.74 mN with rotating magnetic field has been proposed and successfully developed for future applications to low altitude nanosatellites. The key technology issue is that the rotating speed is set above the ion plasma frequency but far below the electron plasma frequency, in order to produce the electron drag current and axial electric field as a consequence of the interaction with the bias field. The formation of axial electric field was confirmed and the produced plasma density was >6×1018 m-3, whereas the power consumption is 500 W in the inductively coupled mode of operation. The anticipated thrust density and specific thrust could potentially be extended to 7.64 Nm-2 and 850 s, respectively, which is comparable to conventional Hall effect thrusters.

  12. Compact and Rugged Transceiver for Coherent Doppler Wind Lidar Applications in Space

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Koch, Grady J.; Yu, Jirong; Amzajerdian, Farzin; Singh, Upendra N.; Trieu, Bo C.; Modlin, Ed A.; Petros, Mulugeta; Bai, Yingxin; Reithmaier, Karl; Petzar, Paul J.

    2007-01-01

    High-accuracy, vertical profiles of the horizontal vector wind in earth s atmosphere, with the global coverage of an orbiting sensor, are a highly desired measurement of NASA, NOAA, and many other agencies and countries. It is the consensus of NASA and NOAA that the most cost effective, lowest risk measurement method with the earliest achievable mission date is the hybrid Doppler lidar method which utilizes both coherent- and direct-detection Doppler lidars to obtain the desired profiles. NASA Langley Research Center (LaRC) has advanced the 2-micron pulsed solid-state laser greatly over the past 15 years and has recently demonstrated 1.2 J of pulse energy whereas the requirement for a 400-km hybrid Doppler lidar mission is only 0.25 J. The IIP project reported here is an effort to increase the ruggedness and to compactly package the LaRC state-of-the-art laser technology.

  13. A Compact Disk Type Plasma Propulsion System with Modulated Magnetic Field for Nanoscale Space Vehicles

    SciTech Connect

    Fukuda, Takeshi; Ueda, Satoshi; Ohnishi, Yukihiro; Inomoto, Michiaki

    2008-12-31

    A compact 5 mm disk type plasma thruster simply composed of only a set of antenna windings and bias field coil which produces significant thrust of 0.74 mN with rotating magnetic field has been proposed and successfully developed for future applications to low altitude nanosatellites. The key technology issue is that the rotating speed is set above the ion plasma frequency but far below the electron plasma frequency, in order to produce the electron drag current and axial electric field as a consequence of the interaction with the bias field. The formation of axial electric field was confirmed and the produced plasma density was >6x10{sup 18} m{sup -3}, whereas the power consumption is 500 W in the inductively coupled mode of operation. The anticipated thrust density and specific thrust could potentially be extended to 7.64 Nm{sup -2} and 850 s, respectively, which is comparable to conventional Hall effect thrusters.

  14. Measurement of Insulation Compaction in the Cryogenic Fuel Tanks at Kennedy Space Center by Fast/Thermal Neutron Techniques

    NASA Technical Reports Server (NTRS)

    Livingston, R. A.; Schweitzer, J. S.; Parsons, Ann M.; Arens, Ellen E.

    2010-01-01

    The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Th ere is evidence that some of the perlite has compacted over time, com promising the thermal performance and possibly also structural integr ity of the tanks. Therefore an Non-destructive Testing (NDT) method for measuring the perlite density or void fraction is urgently needed. Methods based on neutrons are good candidates because they can readil y penetrate through the 1.75 cm outer steel shell and through the ent ire 120 cm thickness of the perlite zone. Neutrons interact with the nuclei of materials to produce characteristic gamma rays which are the n detected. The gamma ray signal strength is proportional to the atom ic number density. Consequently, if the perlite is compacted then the count rates in the individual peaks in the gamma ray spectrum will i ncrease. Perlite is a feldspathic volcanic rock made up of the major elements Si, AI, Na, K and 0 along with some water. With commercially available portable neutron generators it is possible to produce simul taneously fluxes of neutrons in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scatt ering which is sensitive to Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA) and this is sensitive to Si, AI, Na, Kand H. Thus the two energy ranges produce complementary information. The R&D program has three phases: numerical simulations of neutron and gamma ray transport with MCNP s oftware, evaluation of the system in the laboratory on test articles and finally mapping of the perlite density in the cryogenic tanks at KSC. The preliminary MCNP calculations have shown that the fast/therma l neutron NDT method is capable of distinguishing between expanded an d compacted perlite with excellent statistics.

  15. CONFIRMATION OF THE COMPACTNESS OF A z = 1.91 QUIESCENT GALAXY WITH HUBBLE SPACE TELESCOPE'S WIDE FIELD CAMERA 3

    SciTech Connect

    Szomoru, Daniel; Franx, Marijn; Bouwens, Rychard J.; Van Dokkum, Pieter G.; Trenti, Michele; Illingworth, Garth D.; Oesch, Pascal A.; Carollo, C. Marcella

    2010-05-10

    We present very deep Wide Field Camera 3 (WFC3) photometry of a massive, compact galaxy located in the Hubble Ultra Deep Field. This quiescent galaxy has a spectroscopic redshift z = 1.91 and has been identified as an extremely compact galaxy by Daddi et al. We use new H {sub F160W} imaging data obtained with Hubble Space Telescope/WFC3 to measure the deconvolved surface brightness profile to H {approx} 28 mag arcsec{sup -2}. We find that the surface brightness profile is well approximated by an n = 3.7 Sersic profile. Our deconvolved profile is constructed by a new technique which corrects the best-fit Sersic profile with the residual of the fit to the observed image. This allows for galaxy profiles which deviate from a Sersic profile. We determine the effective radius of this galaxy: r{sub e} = 0.42 {+-} 0.14 kpc in the observed H {sub F160W} band. We show that this result is robust to deviations from the Sersic model used in the fit. We test the sensitivity of our analysis to faint 'wings' in the profile using simulated galaxy images consisting of a bright compact component and a faint extended component. We find that due to the combination of the WFC3 imaging depth and our method's sensitivity to extended faint emission we can accurately trace the intrinsic surface brightness profile, and that we can therefore confidently rule out the existence of a faint extended envelope around the observed galaxy down to our surface brightness limit. These results confirm that the galaxy lies a factor {approx}10 off from the local mass-size relation.

  16. Development of a Compact Efficient Cooling Pump for Space Suit Life Support Systems

    NASA Technical Reports Server (NTRS)

    vanBoeyen, Roger W.; Reeh, Jonathan A.; Trevino, Luis

    2008-01-01

    With the increasing demands placed on extravehicular activity (EVA) for the International Space Station (ISS) assembly and maintenance, along with planned lunar and Martian missions, the need for increased human productivity and capability becomes ever more critical. This is most readily achieved by reduction in space suit weight and volume, and increased hardware reliability, durability, and operating lifetime. Considerable progress has been made with each successive generation of space suit design; from the Apollo A7L suit, to the current Shuttle Extravehicular Mobile Unit (EMU) suit, and the next generation Constellation Space Suit Element (CSSE). However, one area of space suit design which has continued to lag is the fluid pump used to drive the water cooling loop of the Primary Life Support System (PLSS). The two main types of fluid pumps typically used in space applications are rotodynamic pumps (pumping is achieved through a rotary vaned impeller) and displacement pumps (which includes rotary and diaphragm pumps). The rotating and moving parts found in the pumps and electric motor add significantly to the susceptibility to wear and friction, thermal mismatch, and complexity of the pumps. Electric motor-driven pumps capable of achieving high operational reliability are necessarily large, heavy, and energy inefficient. This report describes a development effort conducted for NASA by Lynntech, Inc., who recently demonstrated the feasibility of an electrochemically-driven fluid cooling pump. With no electric motor and minimal lightweight components, an electrochemically-driven pump is expected to be significantly smaller, lighter and achieve a longer life time than conventional rotodynamic and displacement pumps. By employing sulfonated polystyrene-based proton exchange membranes, rather than conventional Nafion membranes, a significant reduction in the actuator power consumption was demonstrated. It was also demonstrated that these membranes possess the

  17. Compact optical transmitters for CubeSat free-space optical communications

    NASA Astrophysics Data System (ADS)

    Kingsbury, R. W.; Caplan, D. O.; Cahoy, K. L.

    2015-03-01

    We present the results of an architectural trade study and prototype implementation of an optical transmitter suitable for resource-constrained CubeSats. Recent advances in CubeSat attitude determination and control systems have made it possible to achieve three-axis stabilization. This is essential for laser communications systems, which have challenging pointing and stability requirements. Our downlink terminal design fits in a 10 cm x 10 cm x 5 cm volume, uses < 10W of power, weighs < 1 kg, and supports data rates up to 50 Mbps. The terminal incorporates pointing, tracking and acquisition optics, an optical fine-steering mechanism, and a compact transmitter. This work focuses on the development of the transmitter for the Nanosatellite Optical Downlink Experiment (NODE). Two transmitter architectures were considered initially: direct modulation of a high-power laser diode and a master oscillator power amplifier (MOPA). The MOPA-based approach was selected and a prototype "breadboard" was built from commercially available components. The prototype transmitter produces high fidelity (extinction ratio, ER < 33 dB) pulse position modulation (PPM) waveforms at 1550nm with 200mW average output power while consuming 6:5W of electrical power.

  18. On a fourth order accurate implicit finite difference scheme for hyperbolic conservation laws. II - Five-point schemes

    NASA Technical Reports Server (NTRS)

    Harten, A.; Tal-Ezer, H.

    1981-01-01

    This paper presents a family of two-level five-point implicit schemes for the solution of one-dimensional systems of hyperbolic conservation laws, which generalized the Crank-Nicholson scheme to fourth order accuracy (4-4) in both time and space. These 4-4 schemes are nondissipative and unconditionally stable. Special attention is given to the system of linear equations associated with these 4-4 implicit schemes. The regularity of this system is analyzed and efficiency of solution-algorithms is examined. A two-datum representation of these 4-4 implicit schemes brings about a compactification of the stencil to three mesh points at each time-level. This compact two-datum representation is particularly useful in deriving boundary treatments. Numerical results are presented to illustrate some properties of the proposed scheme.

  19. On the superconvergence of Galerkin methods for hyperbolic IBVP

    NASA Technical Reports Server (NTRS)

    Gottlieb, David; Gustafsson, Bertil; Olsson, Pelle; Strand, BO

    1993-01-01

    Finite element Galerkin methods for periodic first order hyperbolic equations exhibit superconvergence on uniform grids at the nodes, i.e., there is an error estimate 0(h(sup 2r)) instead of the expected approximation order 0(h(sup r)). It will be shown that no matter how the approximating subspace S(sup h) is chosen, the superconvergence property is lost if there are characteristics leaving the domain. The implications of this result when constructing compact implicit difference schemes is also discussed.

  20. Hyperbolic Metamaterials with Bragg Polaritons.

    PubMed

    Sedov, Evgeny S; Iorsh, I V; Arakelian, S M; Alodjants, A P; Kavokin, Alexey

    2015-06-12

    We propose a novel mechanism for designing quantum hyperbolic metamaterials with the use of semiconductor Bragg mirrors containing periodically arranged quantum wells. The hyperbolic dispersion of exciton-polariton modes is realized near the top of the first allowed photonic miniband in such a structure which leads to the formation of exciton-polariton X waves. Exciton-light coupling provides a resonant nonlinearity which leads to nontrivial topologic solutions. We predict the formation of low amplitude spatially localized oscillatory structures: oscillons described by kink shaped solutions of the effective Ginzburg-Landau-Higgs equation. The oscillons have direct analogies in gravitational theory. We discuss implementation of exciton-polariton Higgs fields for the Schrödinger cat state generation. PMID:26196825

  1. Fluctuational electrodynamics of hyperbolic metamaterials

    SciTech Connect

    Guo, Yu; Jacob, Zubin

    2014-06-21

    We give a detailed account of equilibrium and non-equilibrium fluctuational electrodynamics of hyperbolic metamaterials. We show the unifying aspects of two different approaches; one utilizes the second kind of fluctuation dissipation theorem and the other makes use of the scattering method. We analyze the near-field of hyperbolic media at finite temperatures and show that the lack of spatial coherence can be attributed to the multi-modal nature of super-Planckian thermal emission. We also adopt the analysis to phonon-polaritonic super-lattice metamaterials and describe the regimes suitable for experimental verification of our predicted effects. The results reveal that far-field thermal emission spectra are dominated by epsilon-near-zero and epsilon-near-pole responses as expected from Kirchoff's laws. Our work should aid both theorists and experimentalists to study complex media and engineer equilibrium and non-equilibrium fluctuations for applications in thermal photonics.

  2. Visible-frequency hyperbolic metasurface.

    PubMed

    High, Alexander A; Devlin, Robert C; Dibos, Alan; Polking, Mark; Wild, Dominik S; Perczel, Janos; de Leon, Nathalie P; Lukin, Mikhail D; Park, Hongkun

    2015-06-11

    Metamaterials are artificial optical media composed of sub-wavelength metallic and dielectric building blocks that feature optical phenomena not present in naturally occurring materials. Although they can serve as the basis for unique optical devices that mould the flow of light in unconventional ways, three-dimensional metamaterials suffer from extreme propagation losses. Two-dimensional metamaterials (metasurfaces) such as hyperbolic metasurfaces for propagating surface plasmon polaritons have the potential to alleviate this problem. Because the surface plasmon polaritons are guided at a metal-dielectric interface (rather than passing through metallic components), these hyperbolic metasurfaces have been predicted to suffer much lower propagation loss while still exhibiting optical phenomena akin to those in three-dimensional metamaterials. Moreover, because of their planar nature, these devices enable the construction of integrated metamaterial circuits as well as easy coupling with other optoelectronic elements. Here we report the experimental realization of a visible-frequency hyperbolic metasurface using single-crystal silver nanostructures defined by lithographic and etching techniques. The resulting devices display the characteristic properties of metamaterials, such as negative refraction and diffraction-free propagation, with device performance greatly exceeding those of previous demonstrations. Moreover, hyperbolic metasurfaces exhibit strong, dispersion-dependent spin-orbit coupling, enabling polarization- and wavelength-dependent routeing of surface plasmon polaritons and two-dimensional chiral optical components. These results open the door to realizing integrated optical meta-circuits, with wide-ranging applications in areas from imaging and sensing to quantum optics and quantum information science. PMID:26062510

  3. Geometric proof for normally hyperbolic invariant manifolds

    NASA Astrophysics Data System (ADS)

    Capiński, Maciej J.; Zgliczyński, Piotr

    2015-12-01

    We present a new proof of the existence of normally hyperbolic manifolds and their whiskers for maps. Our result is not perturbative. Based on the bounds on the map and its derivative, we establish the existence of the manifold within a given neighborhood. Our proof follows from a graph transform type method and is performed in the state space of the system. We do not require the map to be invertible. From our method follows also the smoothness of the established manifolds, which depends on the smoothness of the map, as well as rate conditions, which follow from bounds on the derivative of the map. Our method is tailor made for rigorous, interval arithmetic based, computer assisted validation of the needed assumptions.

  4. Coincidence lattices in the hyperbolic plane.

    PubMed

    Rodríguez-Andrade, M A; Aragón-González, G; Aragón, J L; Gómez-Rodríguez, A

    2011-01-01

    The problem of coincidences of lattices in the space R(p,q), with p + q = 2, is analyzed using Clifford algebra. We show that, as in R(n), any coincidence isometry can be decomposed as a product of at most two reflections by vectors of the lattice. Bases and coincidence indices are constructed explicitly for several interesting lattices. Our procedure is metric-independent and, in particular, the hyperbolic plane is obtained when p = q = 1. Additionally, we provide a proof of the Cartan-Dieudonné theorem for R(p,q), with p + q = 2, that includes an algorithm to decompose an orthogonal transformation into a product of reflections. PMID:21173471

  5. Traffic noise and the hyperbolic plane

    SciTech Connect

    Gibbons, G.W. Warnick, C.M.

    2010-04-15

    We consider the problem of sound propagation in a wind. We note that the rays, as in the absence of a wind, are given by Fermat's principle and show how to map them to the trajectories of a charged particle moving in a magnetic field on a curved space. For the specific case of sound propagating in a stratified atmosphere with a small wind speed, we show that the corresponding particle moves in a constant magnetic field on the hyperbolic plane. In this way, we give a simple 'straightedge and compass' method to estimate the intensity of sound upwind and downwind. We construct Mach envelopes for moving sources. Finally, we relate the problem to that of finding null geodesics in a squashed anti-de Sitter spacetime and discuss the SO(3,1)xR symmetry of the problem from this point of view.

  6. Mu-Spec - A High Performance Ultra-Compact Photon Counting spectrometer for Space Submillimeter Astronomy

    NASA Technical Reports Server (NTRS)

    Moseley, H.; Hsieh, W.-T.; Stevenson, T.; Wollack, E.; Brown, A.; Benford, D.; Sadleir; U-Yen, I.; Ehsan, N.; Zmuidzinas, J.; Bradford, M.

    2011-01-01

    We have designed and are testing elements of a fully integrated submillimeter spectrometer based on superconducting microstrip technology. The instrument can offer resolving power R approximately 1500, and its high frequency cutoff is set by the gap of available high performance superconductors. All functions of the spectrometer are integrated - light is coupled to the microstrip circuit with a planar antenna, the spectra discrimination is achieved using a synthetic grating, orders are separated using planar filter, and detected using photon counting MKID detector. This spectrometer promises to revolutionize submillimeter spectroscopy from space. It replaces instruments with the scale of 1m with a spectrometer on a 10 cm Si wafer. The reduction in mass and volume promises a much higher performance system within available resource in a space mission. We will describe the system and the performance of the components that have been fabricated and tested.

  7. Calibration of the Compact Environmental Anomaly Sensor (CEASE) for the DSX space weather mission

    NASA Astrophysics Data System (ADS)

    Dichter, Bronislaw K.; McGarity, John; Mullen, E. G.; Brautigam, Donald; Galica, Gary E.; Golightly, Michael J.

    2009-08-01

    The CEASE instrument was designed to measure energetic electrons and protons in the space environment. It consists of two dosimeter detectors, a particle telescope and a Single Event Effect rate detector. CEASE was designed to be an engineering instrument providing real-time warnings of space weather hazards to the spacecraft operators. The Air Force Research Laboratory has flown CEASE instruments on two long term missions and is using the data as a part of its radiation belt model research. A third CEASE instrument will be flown on the Air Force Research Laboratory DSX mission. The method and results of the calibration of the particle telescope sensor on CEASE will be presented. An extensive program of telescope response simulation calculations has also been carried out using both simple analytical models and the Monte Carlo particle interaction codes, MCNPX and Integrated TIGER Series. Comparison of calculated telescope results to the measured calibration data will be presented.

  8. Instrumented roll technology for the design space development of roller compaction process.

    PubMed

    Nesarikar, Vishwas V; Vatsaraj, Nipa; Patel, Chandrakant; Early, William; Pandey, Preetanshu; Sprockel, Omar; Gao, Zhihui; Jerzewski, Robert; Miller, Ronald; Levin, Michael

    2012-04-15

    Instrumented roll technology on Alexanderwerk WP120 roller compactor was developed and utilized successfully for the measurement of normal stress on ribbon during the process. The effects of process parameters such as roll speed (4-12 rpm), feed screw speed (19-53 rpm), and hydraulic roll pressure (40-70 bar) on normal stress and ribbon density were studied using placebo and active pre-blends. The placebo blend consisted of 1:1 ratio of microcrystalline cellulose PH102 and anhydrous lactose with sodium croscarmellose, colloidal silicon dioxide, and magnesium stearate. The active pre-blends were prepared using various combinations of one active ingredient (3-17%, w/w) and lubricant (0.1-0.9%, w/w) levels with remaining excipients same as placebo. Three force transducers (load cells) were installed linearly along the width of the roll, equidistant from each other with one transducer located in the center. Normal stress values recorded by side sensors and were lower than normal stress values recorded by middle sensor and showed greater variability than middle sensor. Normal stress was found to be directly proportional to hydraulic pressure and inversely to screw to roll speed ratio. For active pre-blends, normal stress was also a function of compressibility. For placebo pre-blends, ribbon density increased as normal stress increased. For active pre-blends, in addition to normal stress, ribbon density was also a function of gap. Models developed using placebo were found to predict ribbon densities of active blends with good accuracy and the prediction error decreased as the drug concentration of active blend decreased. Effective angle of internal friction and compressibility properties of active pre blend may be used as key indicators for predicting ribbon densities of active blend using placebo ribbon density model. Feasibility of on-line prediction of ribbon density during roller compaction was demonstrated using porosity-pressure data of pre-blend and normal stress

  9. Vibration and stress analysis of soft-bonded shuttle insulation tiles. Modal analysis with compact widely space stringers

    NASA Technical Reports Server (NTRS)

    Ojalvo, I. U.; Austin, F.; Levy, A.

    1974-01-01

    An efficient iterative procedure is described for the vibration and modal stress analysis of reusable surface insulation (RSI) of multi-tiled space shuttle panels. The method, which is quite general, is rapidly convergent and highly useful for this application. A user-oriented computer program based upon this procedure and titled RESIST (REusable Surface Insulation Stresses) has been prepared for the analysis of compact, widely spaced, stringer-stiffened panels. RESIST, which uses finite element methods, obtains three dimensional tile stresses in the isolator, arrestor (if any) and RSI materials. Two dimensional stresses are obtained in the tile coating and the stringer-stiffened primary structure plate. A special feature of the program is that all the usual detailed finite element grid data is generated internally from a minimum of input data. The program can accommodate tile idealizations with up to 850 nodes (2550 degrees-of-freedom) and primary structure idealizations with a maximum of 10,000 degrees-of-freedom. The primary structure vibration capability is achieved through the development of a new rapid eigenvalue program named ALARM (Automatic LArge Reduction of Matrices to tridiagonal form).

  10. Convergence of Lax-Friedrichs and Godunov schemes for a nonstrictly hyperbolic system of conservation laws arising in oil recovery

    NASA Astrophysics Data System (ADS)

    Djoufedie, George Noel; Felaco, Elisabetta; Rubino, Bruno; Sampalmieri, Rosella

    2016-03-01

    This paper is devoted to the compactness framework and the convergence theorem for the Lax-Friedrichs and Godunov schemes applied to a {2 × 2} system of non-strictly hyperbolic nonlinear conservation laws that arises from mathematical models for oil recovery. The presence of a degeneracy in the hyperbolicity of the system requires a careful analysis of the entropy functions, whose regularity is necessary to obtain the result. For this purpose, it is necessary to combine the classical techniques referring to a singular Euler-Poisson-Darboux equation with the compensated compactness method.

  11. A Compact Infrared Space Telescope MIRIS and its Preliminary Observational Results

    NASA Astrophysics Data System (ADS)

    Han, Wonyong; Pyo, Jeonghyun; Kim, Il-Joong; Lee, Dae-Hee; Jeong, Woong-Seob; Moon, Bongkon; Park, Youngsik; Park, Sung-Joon; Lee, Dukhang; Park, Won-Kee; Ko, Kyeongyeon; Kim, Min Gyu; Nam, Uk-Won; Park, Hong-Young; Lee, Hyung Mok; Matsumoto, Toshio

    2015-08-01

    The first Korean infrared space telescope MIRIS (Milti-purpose InfraRed Imaging System) was successfully launched in November 2013, as the main payload of Korean STSAT-3 (Science and Technology Satellite-3). After the initial on-orbit operation for verification, the observations are made with MIRIS for the fluctuation of Cosmic Infrared Background (CIB) and the Galactic Plane survey. For the study of near-infrared background, MIRIS surveyed large areas (> 10° x 10°) around the pole regions: the north ecliptic pole (NEP), the north and south Galactic poles (NGP, SGP), while the NEP region is continually monitored for the instrumental calibration and the zodiacal light study. In addition, the Paschen-α Galactic plane survey has been made with two narrow-band filters (at 1.88 μm and 1.84+1.92 μm) for the study of warm interstellar medium. We plan to continue surveying the entire galactic plane with the latitude of ±3°, and expect to be completed by 2015. The data are still under the stage of reduction and analysis, and guest observations are on-going. We present some of the preliminary results.

  12. Seniority number in spin-adapted spaces and compactness of configuration interaction wave functions.

    PubMed

    Alcoba, Diego R; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E; Oña, Ofelia B

    2013-08-28

    This work extends the concept of seniority number, which has been widely used for classifying N-electron Slater determinants, to wave functions of N electrons and spin S, as well as to N-electron spin-adapted Hilbert spaces. We propose a spin-free formulation of the seniority number operator and perform a study on the behavior of the expectation values of this operator under transformations of the molecular basis sets. This study leads to propose a quantitative evaluation for the convergence of the expansions of the wave functions in terms of Slater determinants. The non-invariant character of the seniority number operator expectation value of a wave function with respect to a unitary transformation of the molecular orbital basis set, allows us to search for a change of basis which minimizes that expectation value. The results found in the description of wave functions of selected atoms and molecules show that the expansions expressed in these bases exhibit a more rapid convergence than those formulated in the canonical molecular orbital bases and even in the natural orbital ones. PMID:24006970

  13. Seniority number in spin-adapted spaces and compactness of configuration interaction wave functions

    NASA Astrophysics Data System (ADS)

    Alcoba, Diego R.; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E.; Oña, Ofelia B.

    2013-08-01

    This work extends the concept of seniority number, which has been widely used for classifying N-electron Slater determinants, to wave functions of N electrons and spin S, as well as to N-electron spin-adapted Hilbert spaces. We propose a spin-free formulation of the seniority number operator and perform a study on the behavior of the expectation values of this operator under transformations of the molecular basis sets. This study leads to propose a quantitative evaluation for the convergence of the expansions of the wave functions in terms of Slater determinants. The non-invariant character of the seniority number operator expectation value of a wave function with respect to a unitary transformation of the molecular orbital basis set, allows us to search for a change of basis which minimizes that expectation value. The results found in the description of wave functions of selected atoms and molecules show that the expansions expressed in these bases exhibit a more rapid convergence than those formulated in the canonical molecular orbital bases and even in the natural orbital ones.

  14. Minimality of invariant laminations for partially hyperbolic attractors

    NASA Astrophysics Data System (ADS)

    Nobili, Felipe

    2015-06-01

    Let f : M → M be a C1-diffeomorphism over a compact boundaryless Riemannian manifold M, and Λ a compact f-invariant subset of M admitting a partially hyperbolic spliting TfΛ = Es ⊕ Ec ⊕ Eu over the tangent bundle TfΛ. It's known from the Hirsch-Pugh-Shub theory that Λ admits two invariant laminations associated to the extremal bundles Es and Eu. These laminations are families of dynamically defined immersed submanifolds of the M tangent, respectively, to the bundles Es and Eu at every point in Λ. In this work, we prove that at least one of the invariant laminations of a transitive partially hyperbolic attractor with a one-dimensional center bundle is minimal: the orbit of every leaf intersects Λ densely. This result extends those in Bonatti et al (2002 J. Inst. Math. Jussieu 1 513-41) and Hertz et al (2007 Fields Institute Communications vol 51 (Providence, RI: American Mathematical Society) pp 103-9) about minimal foliations for robustly transitive diffeomorphisms.

  15. A low-energy charged particle distribution imager with a compact sensor for space applications

    NASA Astrophysics Data System (ADS)

    Knudsen, D. J.; Burchill, J. K.; Berg, K.; Cameron, T.; Enno, G. A.; Marcellus, C. G.; King, E. P.; Wevers, I.; King, R. A.

    2003-01-01

    Low-energy plasmas having temperatures of order 1 eV or less are found commonly in the ionospheres and space environments of Earth and other planets. Measuring the density, temperature, drift velocities, phase-space anisotropies, and other properties of these plasmas presents numerous challenges. Examples are distortions of particle trajectories due to spacecraft wakes, spacecraft charging, and particle gyromotion in magnetized plasmas. Furthermore, these plasmas are known to organize into structures as small as tens of meters across, traversed by spacecraft in tens of milliseconds or less. The Suprathermal Plasma Imager (SPI) was developed to address these challenges. The SPI is optimized for measurements of particles with ~1 eV energies, and of the suprathermal extension of those populations up to several hundred eV. The SPI is sensitive to particle flux intensities of order 6×105 cm-2 s-1 sr-1 eV-1 and greater. It produces 3024-pixel images corresponding to two-dimensional (angle/energy) cuts through plasma velocity distribution functions, with an image frame rate of up to 100 s-1. The SPI has a cylindrical sensor head measuring 37.5 mm in diameter and 14 cm long, with a mass of 350 g. The relatively small size and mass of the sensor allow it to be deployed easily on a boom, outside of the spacecraft's electrical sheath and in a region where wake perturbations are reduced. The SPI sensor head contains no electronic circuitry, but instead creates a visible image of the particle distribution with a system of dc-biased grids, microchannel plates, and a phosphor screen. The phosphor image is transferred via an imaging fiber-optic cable to an instrument box in the main spacecraft body, where it is sampled with a charge-coupled device and support electronics. Inside the sensor, angle/energy images of incident particle distributions are formed by a pair of concentric hemispherical grids. The incident energies Ei accessible to the analyzer lie in the range 0<=Ei

  16. Second- and third-order upwind difference schemes for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Yang, J. Y.

    1984-01-01

    Second- and third-order two time-level five-point explicit upwind-difference schemes are described for the numerical solution of hyperbolic systems of conservation laws and applied to the Euler equations of inviscid gas dynamics. Nonliner smoothing techniques are used to make the schemes total variation diminishing. In the method both hyperbolicity and conservation properties of the hyperbolic conservation laws are combined in a very natural way by introducing a normalized Jacobian matrix of the hyperbolic system. Entropy satisfying shock transition operators which are consistent with the upwind differencing are locally introduced when transonic shock transition is detected. Schemes thus constructed are suitable for shockcapturing calculations. The stability and the global order of accuracy of the proposed schemes are examined. Numerical experiments for the inviscid Burgers equation and the compressible Euler equations in one and two space dimensions involving various situations of aerodynamic interest are included and compared.

  17. Mid-infrared nanophotonics: Probing hyperbolic polaritons

    NASA Astrophysics Data System (ADS)

    Caldwell, Joshua D.; Vurgaftman, Igor; Tischler, Joseph G.

    2015-10-01

    Hyperbolic phonon polaritons confined to the subdiffraction limit exhibit encouragingly long lifetimes and group velocities as slow as 0.002c. Researchers use a time-resolved set-up sensitive to nanometre-scale optical fields to shed light on the exciting optical properties of hyperbolic materials.

  18. An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

    SciTech Connect

    Desai, M. I.; McComas, D. J.; Allegrini, F.; Livi, S. A.; Ogasawara, K.; Ebert, R. W.; Weidner, S. E.; Alexander, N.

    2015-05-15

    We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ∼10 eV/q–40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ∼30 keV–10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs’ singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

  19. An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

    NASA Astrophysics Data System (ADS)

    Desai, M. I.; Ogasawara, K.; Ebert, R. W.; McComas, D. J.; Allegrini, F.; Weidner, S. E.; Alexander, N.; Livi, S. A.

    2015-05-01

    We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ˜10 eV/q-40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ˜30 keV-10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs' singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

  20. High Gene Family Turnover Rates and Gene Space Adaptation in the Compact Genome of the Carnivorous Plant Utricularia gibba.

    PubMed

    Carretero-Paulet, Lorenzo; Librado, Pablo; Chang, Tien-Hao; Ibarra-Laclette, Enrique; Herrera-Estrella, Luis; Rozas, Julio; Albert, Victor A

    2015-05-01

    Utricularia gibba is an aquatic carnivorous plant with highly specialized morphology, featuring fibrous floating networks of branches and leaf-like organs, no recognizable roots, and bladder traps that capture and digest prey. We recently described the compressed genome of U. gibba as sufficient to control the development and reproduction of a complex organism. We hypothesized intense deletion pressure as a mechanism whereby most noncoding DNA was deleted, despite evidence for three independent whole-genome duplications (WGDs). Here, we explore the impact of intense genome fractionation in the evolutionary dynamics of U. gibba's functional gene space. We analyze U. gibba gene family turnover by modeling gene gain/death rates under a maximum-likelihood statistical framework. In accord with our deletion pressure hypothesis, we show that the U. gibba gene death rate is significantly higher than those of four other eudicot species. Interestingly, the gene gain rate is also significantly higher, likely reflecting the occurrence of multiple WGDs and possibly also small-scale genome duplications. Gene ontology enrichment analyses of U. gibba-specific two-gene orthogroups, multigene orthogroups, and singletons highlight functions that may represent adaptations in an aquatic carnivorous plant. We further discuss two homeodomain transcription factor gene families (WOX and HDG/HDZIP-IV) showing conspicuous differential expansions and contractions in U. gibba. Our results 1) reconcile the compactness of the U. gibba genome with its accommodation of a typical number of genes for a plant genome, and 2) highlight the role of high gene family turnover in the evolutionary diversification of U. gibba's functional gene space and adaptations to its unique lifestyle and highly specialized body plan. PMID:25637935

  1. The art and science of hyperbolic tessellations.

    PubMed

    Van Dusen, B; Taylor, R P

    2013-04-01

    The visual impact of hyperbolic tessellations has captured artists' imaginations ever since M.C. Escher generated his Circle Limit series in the 1950s. The scaling properties generated by hyperbolic geometry are different to the fractal scaling properties found in nature's scenery. Consequently, prevalent interpretations of Escher's art emphasize the lack of connection with nature's patterns. However, a recent collaboration between the two authors proposed that Escher's motivation for using hyperbolic geometry was as a method to deliberately distort nature's rules. Inspired by this hypothesis, this year's cover artist, Ben Van Dusen, embeds natural fractals such as trees, clouds and lightning into a hyperbolic scaling grid. The resulting interplay of visual structure at multiple size scales suggests that hybridizations of fractal and hyperbolic geometries provide a rich compositional tool for artists. PMID:23517611

  2. Frequency of hyperbolic and interstellar meteoroids

    NASA Astrophysics Data System (ADS)

    Hajduková, Maria; Kornoš, Leonard; Tóth, Juraj

    2014-01-01

    Hyperbolic meteor orbits from the catalog of 64,650 meteors observed by the multistation video meteor network located in Japan (SonotaCo 2009) have been investigated with the aim of determining the relation between the frequency of hyperbolic and interstellar meteors. The proportion of hyperbolic meteors in the data decreased significantly (from 11.58% to 3.28%) after a selection of quality orbits, which shows its dependence on the quality of observations. Initially, the hyperbolic orbits were searched for meteors unbound due to planetary perturbation. It was determined that 22 meteors from the 7489 hyperbolic orbits in the catalog (and 2 from the selection of the orbits with the highest quality) had had a close encounter with a planet, none of which, however, produced essential changes in their orbits. Similarly, the fraction of hyperbolic orbits in the data, which could be hyperbolic by reason of a meteor's interstellar origin, was determined to be at most 3.9 × 10-2. From the statistical point of view, the vast majority of hyperbolic meteors in the database have definitely been caused by inaccuracy in the velocity determination. This fact does not necessarily assume great measurement errors, since, especially near the parabolic limit, a small error in the value of the heliocentric velocity of a meteor can create an artificial hyperbolic orbit that does not really exist. The results show that the remaining 96% of meteoroids with apparent hyperbolic orbits belong to the solar system meteoroid population. This is also supported by their high abundance (about 50%) among the meteor showers.

  3. Comparison of hyperbolic and hyperboloid conductor electrostatics

    NASA Astrophysics Data System (ADS)

    Lekner, John

    2006-01-01

    The potentials and fields of hyperbolic and hyperboloidal conductors are available analytically. A detailed comparison of the two-dimensional and three-dimensional problems shows strong similarities, but also interesting differences. The electric field near a hyperboloidal needle is stronger (ceteris paribus) than near a hyperbolic blade, and dies off faster. The field at the hyperbolic conductor varies as the 1/3 power of the local curvature. At the hyperboloid conductor the field varies as the 1/4 power of the local Gaussian curvature (which is the product of the two principal curvatures).

  4. Scaling of clusters near discontinuous percolation transitions in hyperbolic networks

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Boettcher, Stefan

    2014-07-01

    We investigate the onset of the discontinuous percolation transition in small-world hyperbolic networks by studying the systems-size scaling of the typical largest cluster approaching the transition, p ↗pc. To this end, we determine the average size of the largest cluster ˜NΨ (p) in the thermodynamic limit using real-space renormalization of cluster-generating functions for bond and site percolation in several models of hyperbolic networks that provide exact results. We determine that all our models conform to the recently predicted behavior regarding the growth of the largest cluster, which found diverging, albeit subextensive, clusters spanning the system with finite probability well below pc and at most quadratic corrections to unity in Ψ (p) for p ↗pc. Our study suggests a large universality in the cluster formation on small-world hyperbolic networks and the potential for an alternative mechanism in the cluster formation dynamics at the onset of discontinuous percolation transitions.

  5. Galois Representations Connected with Hyperbolic Curves

    NASA Astrophysics Data System (ADS)

    Voevodskiĭ, V. A.

    1992-06-01

    The author considers Galois group actions on the fundamental groups of curves of hyperbolic type, and proves certain cases of Grothendieck's conjecture about the possibility of recovering a curve from its Galois representation.

  6. Twist transition of nematic hyperbolic hedgehogs.

    PubMed

    James, Richard; Fukuda, Jun-ichi

    2014-04-01

    Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999)], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell. PMID:24827263

  7. Combinatorial and algorithm aspects of hyperbolic polynomials

    SciTech Connect

    Gurvits, Leonid I.

    2004-01-01

    Univariate polynomials with real roots appear quite often in modern combinatorics, especially in the context of integer polytopes. We discovered in this paper rather unexpected and very likely far-reaching connections between hyperbolic polynomials and many classical combinatorial and algorithmic problems. There are still several open problems. The most interesting is a hyperbolic generalization of the van der Waerden conjecture for permanents of doubly stochastic matrices.

  8. Existence of eigenvalues of problem with shift for an equation of parabolic-hyperbolic type

    NASA Astrophysics Data System (ADS)

    Tengayeva, Aizhan; Dildabek, Gulnar

    2016-08-01

    In the present paper, a spectral problem for an operator of parabolic-hyperbolic type of I kind with non-classical boundary conditions is considered. The problem is considered in a standard domain. The parabolic part of the space is a rectangle. And the hyperbolic part of the space coincides with a characteristic triangle. We consider a problem with the local boundary condition in the domain of parabolicity and with the boundary condition with displacement in the domain of hyperbolicity. We prove the strong solvability of the considered problem. The main aim of the paper is the research of spectral properties of the problem. The existence of eigenvalues of the problem is proved.

  9. Toward optical sensing with hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Mackay, Tom G.

    2015-06-01

    A possible means of optical sensing, based on a porous hyperbolic material that is infiltrated by a fluid containing an analyte to be sensed, was theoretically investigated. The sensing mechanism relies on the observation that extraordinary plane waves propagate in the infiltrated hyperbolic material only in directions enclosed by a cone aligned with the optic axis of the infiltrated hyperbolic material. The angle this cone subtends to the plane perpendicular to the optic axis is θc. The sensitivity of θc to changes in the refractive index of the infiltrating fluid, namely nb, was explored; also considered were the permittivity parameters and porosity of the hyperbolic material, as well as the shape and size of its pores. Sensitivity was gauged by the derivative dθc/dnb. In parametric numerical studies, values of dθc/dnb in excess of 500 deg per refractive index unit were computed, depending upon the constitutive parameters of the porous hyperbolic material and infiltrating fluid and the nature of the porosity. In particular, it was observed that exceeding large values of dθc/dnb could be attained as the negative-valued eigenvalue of the infiltrated hyperbolic material approached zero.

  10. Hyperbolic phonon polaritons in hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Dai, Siyuan

    2015-03-01

    Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. While hyperbolic responses are normally achieved with metamaterials, hexagonal boron nitride (hBN) naturally possesses this property due to the anisotropic phonons in the mid-infrared. Using scattering-type scanning near-field optical microscopy, we studied polaritonic phenomena in hBN. We performed infrared nano-imaging of highly confined and low-loss hyperbolic phonon polaritons in hBN. The polariton wavelength was shown to be governed by the hBN thickness according to a linear law persisting down to few atomic layers [Science, 343, 1125-1129 (2014)]. Additionally, we carried out the modification of hyperbolic response in heterostructures comprised of a mononlayer graphene deposited on hBN. Electrostatic gating of the top graphene layer allows for the modification of wavelength and intensity of hyperbolic phonon polaritons in bulk hBN. The physics of the modification originates from the plasmon-phonon coupling in the hyperbolic medium. Furthermore, we demonstrated the ``hyperlens'' for subdiffractional imaging and focusing using a slab of hBN.

  11. Overview of the Performance of the Compact Total Electron Content Sensor (CTECS) on the Space Environmental NanoSatellite Experiment (SENSE)

    NASA Astrophysics Data System (ADS)

    Bishop, R. L.; Hansel, S.; Stoffel, D.; Ping, D.; Bardeen, J.; Chin, A.; Bielat, S.; Mulligan, T. L.

    2014-12-01

    The Air Force's Space & Missile Systems Center (SMC) SENSE mission consists of two identical cubesat buses with space weather payloads. One of the goals of the SENSE mission is to demonstrate the operational potential and usefulness of space weather measurements from a cubesat platform. The payloads on the two cubesats include the Cubesat Tiny Ionospheric Photometer (SRI), Wind Ion Neutral Composite Suite (NRL), and Compact Total Electron Content GPS radio occultation sensor (CTECS). After initial contact with both space vehicles (SV), we were able to confirm successful operation of both CTECS. Because of power issues on SV2, only SV1 has provided consistent data. In this presentation, we present an overview of the CTECS sensor. Then we present initial CTECS data, discuss the data quality, and lessons learned.

  12. A kinetic scheme for the Navier-Stokes equations and high-order methods for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    May, Georg

    This dissertation revolves around algorithm development in the context of numerical methods for hyperbolic conservation laws and the compressible Navier-Stokes equations, with particular emphasis on unstructured meshes. Three distinct topics may be identified: Firstly, a new kinetic scheme for the compressible Navier-Stokes equations is developed. Kinetic numerical schemes are based on the discretization of a probability density function. In the context of fluid flow such schemes have a natural basis rooted in the kinetic theory of gases. A significant advantage of kinetic schemes is that they allow a compact, completely mesh-independent discretization of the Navier-Stokes equations, which makes them well suited for next-generation solvers on general unstructured meshes. The new kinetic scheme is based on the Xu-Prenderaast BGK scheme, and achieves a dramatic reduction in computational cost, while also improving and clarifying the formulation with respect to the underlying kinetic gas theory. The second topic addresses high-order numerical methods for conservation laws on unstructured meshes. High-order methods potentially produce higher accuracy with fewer degrees of freedom, compared to standard first or second order accurate schemes, while formulation for unstructured meshes makes complex computational domains amenable. The Spectral Difference Method offers a remarkably simple alternative to such high-order schemes for unstructured meshes as the Discontinuous Galerkin and Spectral Volume Methods. Significant contributions to the development of the Spectral Difference Method are presented, including stability analysis, viscous formulation, and h/p-multigrid convergence acceleration. Finally, the theory of Gibbs-complementary reconstruction is utilized in the context of high-order numerical methods for hyperbolic equations. Gibbs-complementary reconstruction makes it possible to extract pointwise high-order convergence in the spectral approximation of non

  13. Triangle based TVD schemes for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Durlofsky, Louis J.; Osher, Stanley; Engquist, Bjorn

    1990-01-01

    A triangle based total variation diminishing (TVD) scheme for the numerical approximation of hyperbolic conservation laws in two space dimensions is constructed. The novelty of the scheme lies in the nature of the preprocessing of the cell averaged data, which is accomplished via a nearest neighbor linear interpolation followed by a slope limiting procedures. Two such limiting procedures are suggested. The resulting method is considerably more simple than other triangle based non-oscillatory approximations which, like this scheme, approximate the flux up to second order accuracy. Numerical results for linear advection and Burgers' equation are presented.

  14. Minimal dissipation hybrid bicompact schemes for hyperbolic equations

    NASA Astrophysics Data System (ADS)

    Bragin, M. D.; Rogov, B. V.

    2016-06-01

    New monotonicity-preserving hybrid schemes are proposed for multidimensional hyperbolic equations. They are convex combinations of high-order accurate central bicompact schemes and upwind schemes of first-order accuracy in time and space. The weighting coefficients in these combinations depend on the local difference between the solutions produced by the high- and low-order accurate schemes at the current space-time point. The bicompact schemes are third-order accurate in time, while having the fourth order of accuracy and the first difference order in space. At every time level, they can be solved by marching in each spatial variable without using spatial splitting. The upwind schemes have minimal dissipation among all monotone schemes constructed on a minimum space-time stencil. The hybrid schemes constructed has been successfully tested as applied to a number of two-dimensional gas dynamics benchmark problems.

  15. MCNP Simulations of Measurement of Insulation Compaction in the Cryogenic Rocket Fuel Tanks at Kennedy Space Center by Fast/Thermal Neutron Techniques

    NASA Technical Reports Server (NTRS)

    Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.; Arens, E. E.

    2010-01-01

    MCNP simulations have been run to evaluate the feasibility of using a combination of fast and thermal neutrons as a nondestructive method to measure of the compaction of the perlite insulation in the liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC). Perlite is a feldspathic volcanic rock made up of the major elements Si, AI, Na, K and 0 along with some water. When heated it expands from four to twenty times its original volume which makes it very useful for thermal insulation. The cryogenic tanks at Kennedy Space Center are spherical with outer diameters of 69-70 feet and lined with a layer of expanded perlite with thicknesses on the order of 120 cm. There is evidence that some of the perlite has compacted over time since the tanks were built 1965, affecting the thermal properties and possibly also the structural integrity of the tanks. With commercially available portable neutron generators it is possible to produce simultaneously fluxes of neutrons in two energy ranges: fast (14 Me V) and thermal (25 me V). The two energy ranges produce complementary information. Fast neutrons produce gamma rays by inelastic scattering, which is sensitive to Fe and O. Thermal neutrons produce gamma rays by prompt gamma neutron activation (PGNA) and this is sensitive to Si, Al, Na, K and H. The compaction of the perlite can be measured by the change in gamma ray signal strength which is proportional to the atomic number densities of the constituent elements. The MCNP simulations were made to determine the magnitude of this change. The tank wall was approximated by a I-dimensional slab geometry with an 11/16" outer carbon steel wall, an inner stainless wall and 120 cm thick perlite zone. Runs were made for cases with expanded perlite, compacted perlite or with various void fractions. Runs were also made to simulate the effect of adding a moderator. Tallies were made for decay-time analysis from t=0 to 10 ms; total detected gamma

  16. Second-order numerical solution of time-dependent, first-order hyperbolic equations

    NASA Technical Reports Server (NTRS)

    Shah, Patricia L.; Hardin, Jay

    1995-01-01

    A finite difference scheme is developed to find an approximate solution of two similar hyperbolic equations, namely a first-order plane wave and spherical wave problem. Finite difference approximations are made for both the space and time derivatives. The result is a conditionally stable equation yielding an exact solution when the Courant number is set to one.

  17. Stability of shock waves for multi-dimensional hyperbolic-parabolic conservation laws

    NASA Astrophysics Data System (ADS)

    Li, Dening

    1988-01-01

    The uniform linear stability of shock waves is considerd for quasilinear hyperbolic-parabolic coupled conservation laws in multi-dimensional space. As an example, the stability condition and its dynamic meaning for isothermal shock wave in radiative hydrodynamics are analyzed.

  18. Invisible Hyperbolic Metamaterial Nanotube at Visible Frequency.

    PubMed

    Kim, Kyoung-Ho; No, You-Shin; Chang, Sehwan; Choi, Jae-Hyuck; Park, Hong-Gyu

    2015-01-01

    Subwavelength-scale metal and dielectric nanostructures have served as important building blocks for electromagnetic metamaterials, providing unprecedented opportunities for manipulating the optical response of the matter. Recently, hyperbolic metamaterials have been drawing particular interest because of their unusual optical properties and functionalities, such as negative refraction and hyperlensing of light. Here, as a promising application of a hyperbolic metamaterial at visible frequency, we propose an invisible nanotube that consists of metal and dielectric alternating thin layers. The theoretical study of the light scattering of the layered nanotube reveals that almost-zero scattering can be achieved at a specific wavelength when the transverse-electric- or transverse-magnetic-polarized light is incident to the nanotube. In addition, the layered nanotube can be described as a radial-anisotropic hyperbolic metamaterial nanotube. The low scattering occurs when the effective permittivity of the hyperbolic nanotube in the angular direction is near zero, and thus the invisibility of the layered nanotube can be efficiently obtained by analyzing the equivalent hyperbolic nanotube. Our new method to design and tune an invisible nanostructure represents a significant step toward the practical implementation of unique nanophotonic devices such as invisible photodetectors and low-scattering near-field optical microscopes. PMID:26522815

  19. Invisible Hyperbolic Metamaterial Nanotube at Visible Frequency

    PubMed Central

    Kim, Kyoung-Ho; No, You-Shin; Chang, Sehwan; Choi, Jae-Hyuck; Park, Hong-Gyu

    2015-01-01

    Subwavelength-scale metal and dielectric nanostructures have served as important building blocks for electromagnetic metamaterials, providing unprecedented opportunities for manipulating the optical response of the matter. Recently, hyperbolic metamaterials have been drawing particular interest because of their unusual optical properties and functionalities, such as negative refraction and hyperlensing of light. Here, as a promising application of a hyperbolic metamaterial at visible frequency, we propose an invisible nanotube that consists of metal and dielectric alternating thin layers. The theoretical study of the light scattering of the layered nanotube reveals that almost-zero scattering can be achieved at a specific wavelength when the transverse-electric- or transverse-magnetic-polarized light is incident to the nanotube. In addition, the layered nanotube can be described as a radial-anisotropic hyperbolic metamaterial nanotube. The low scattering occurs when the effective permittivity of the hyperbolic nanotube in the angular direction is near zero, and thus the invisibility of the layered nanotube can be efficiently obtained by analyzing the equivalent hyperbolic nanotube. Our new method to design and tune an invisible nanostructure represents a significant step toward the practical implementation of unique nanophotonic devices such as invisible photodetectors and low-scattering near-field optical microscopes. PMID:26522815

  20. Experimental comparison of Pressure ratio in Alpha and Gamma Stirling cryocoolers with identical compression space volumes and driven simultaneously by a solitary novel compact mechanism

    NASA Astrophysics Data System (ADS)

    Sant, K. D.; Bapat, S. L.

    2015-12-01

    The cryocooler technology is advancing in different ways at a considerable pace to explore cooler applications in diversified field. Stirling cryocoolers are capable to satisfy the contemporary requirements of a low-capacity cooler. A compact mechanism that can drive Stirling cryocooler with larger stroke and thus enhance the cooler performance is the need of the hour. The increase in the stroke will lead to a higher volumetric efficiency. Hence, a cryocooler with larger stroke will experience higher mass flow rate of the working fluid, thereby increasing its ideal cooling capacity. The novel compact drive mechanism that fulfils this need is a promising option in this regards. It is capable of operating more than one cryocoolers of different Stirling configurations simultaneously. This arrangement makes it possible to compare different Stirling cryocoolers on the basis of pressure ratio obtained experimentally. The preliminary experimental results obtained in this regard are presented here. The initial experimentation is carried out on two Alpha Stirling units driven simultaneously by the novel compact mechanism. The pressure ratio obtained during the initial stages is 1.3538, which is enhanced to 1.417 by connecting the rear volumes of the compressor pistons to each other. The fact that annular leak across the expander pistons due to high pressure ratio affects the cryocooler performance, generates the need to separate the expansion space from bounce space. This introduces a Gamma configuration that is operated simultaneously with one of the existing Alpha units by same drive mechanism and having identical compression space volume. The results obtained for pressure ratio in both these units prove the concept that cooling capacity of Alpha configuration exceeds that of Gamma under similar operating conditions. This has been observed at 14 bar and 20 bar charge pressures during the preliminary experimentation. These results are presented in this paper. Thus, the

  1. Link prediction based on hyperbolic mapping with community structure for complex networks

    NASA Astrophysics Data System (ADS)

    Wang, Zuxi; Wu, Yao; Li, Qingguang; Jin, Fengdong; Xiong, Wei

    2016-05-01

    Link prediction is becoming a concerned topic in the complex network field in recent years. However, the existing link prediction methods are unsatisfactory for processing topological information and have high time complexity. This paper presents a novel method of Link Prediction with Community Structure (LPCS) based on hyperbolic mapping. Different from the existing link prediction methods, to utilize global structure information of the network, LPCS deals with the network from an overall perspective. LPCS takes full advantage of the community structure and its hierarchical organization to map networks into hyperbolic space, and obtains the hyperbolic coordinates which depict the global structure information of the network, then uses hyperbolic distance to describe the similarity between the nodes, finally predicts missing links according to the degree of the similarity between unconnected node pairs. The combination of the hyperbolic geometry framework and the community structure makes LPCS perform well in predicting missing links, and the time complexity of LPCS is linear, which makes LPCS can be applied to handle large scale networks in acceptable time. LPCS outperforms many state-of-the-art link prediction methods in the networks obeying power-law degree distribution.

  2. Hyperbolic metamaterial lens with hydrodynamic nonlocal response.

    PubMed

    Yan, Wei; Mortensen, N Asger; Wubs, Martijn

    2013-06-17

    We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens. PMID:23787690

  3. Mapping AdS to dS spaces and back

    NASA Astrophysics Data System (ADS)

    Di Dato, Adriana; Fröb, Markus B.

    2015-03-01

    We derive a map between Einstein spaces of positive and negative curvature, including scalar matter. Starting from a space of positive curvature with some dimensions compactified on a sphere and analytically continuing the number of compact dimensions, we obtain a space of negative curvature with a compact hyperbolic subspace, and vice versa. Prime examples of such spaces are de Sitter (dS) and anti-de Sitter (AdS) space, as well as black hole spacetimes with (A)dS asymptotics and perturbed versions thereof, which play an important role in holography. This map extends work done by Caldarelli et al., who map asymptotically AdS spaces to Ricci-flat ones. A remarkable result is that the boundary of asymptotically AdS spaces is mapped to a brane in the bulk of de Sitter, and perturbations near the AdS boundary are sourced by a stress tensor confined to this brane. We also calculate the Brown-York stress tensor for the perturbed AdS metric, which turns out to be the negative of the stress tensor on the de Sitter brane. The map can also be used as a solution generator, and we obtain a Kerr/AdS solution with hyperbolic horizon from a known Kerr/dS one.

  4. Congruence Approximations for Entrophy Endowed Hyperbolic Systems

    NASA Technical Reports Server (NTRS)

    Barth, Timothy J.; Saini, Subhash (Technical Monitor)

    1998-01-01

    Building upon the standard symmetrization theory for hyperbolic systems of conservation laws, congruence properties of the symmetrized system are explored. These congruence properties suggest variants of several stabilized numerical discretization procedures for hyperbolic equations (upwind finite-volume, Galerkin least-squares, discontinuous Galerkin) that benefit computationally from congruence approximation. Specifically, it becomes straightforward to construct the spatial discretization and Jacobian linearization for these schemes (given a small amount of derivative information) for possible use in Newton's method, discrete optimization, homotopy algorithms, etc. Some examples will be given for the compressible Euler equations and the nonrelativistic MHD equations using linear and quadratic spatial approximation.

  5. C∗-algebras of Penrose hyperbolic tilings

    NASA Astrophysics Data System (ADS)

    Oyono-Oyono, Hervé; Petite, Samuel

    2011-02-01

    Penrose hyperbolic tilings are tilings of the hyperbolic plane which admit, up to affine transformations a finite number of prototiles. In this paper, we give a complete description of the C∗-algebras and of the K-theory for such tilings. Since the continuous hull of these tilings have no transversally invariant measure, these C∗-algebras are traceless. Nevertheless, harmonic currents give rise to 3-cyclic cocycles and we discuss in this setting a higher-order version of the gap-labeling.

  6. Adult Compacts.

    ERIC Educational Resources Information Center

    Further Education Unit, London (England).

    This bulletin focuses on adult compacts, three-way agreements among employers, potential employees, and trainers to provide the right kind of quality training to meet the employers' requirements. Part 1 is an executive summary of a report of the Adult Compacts Project, which studied three adult compacts in Birmingham and Loughborough, England, and…

  7. On a characteristic of the first eigenvalue of the Dirac operator on compact spin symmetric spaces with a Kähler or Quaternion-Kähler structure

    NASA Astrophysics Data System (ADS)

    Milhorat, Jean-Louis

    2015-04-01

    It is shown that on a compact spin symmetric space with a Kähler or Quaternion-Kähler structure, the first eigenvalue of the Dirac operator is linked to a "lowest" action of the holonomy, given by the fiberwise action on spinors of the canonical forms characterized by this holonomy. The result is also verified for the symmetric space F4 /Spin9, proving that it is valid for all the "possible" holonomies in Berger's list occurring in that context. The proof is based on a characterization of the first eigenvalue of the Dirac operator given in Milhorat (2005) and Milhorat (2006). By the way, we review an incorrect statement in the proof of the first lemma in Milhorat (2005).

  8. Dynamical compactness and sensitivity

    NASA Astrophysics Data System (ADS)

    Huang, Wen; Khilko, Danylo; Kolyada, Sergiĭ; Zhang, Guohua

    2016-05-01

    To link the Auslander point dynamics property with topological transitivity, in this paper we introduce dynamically compact systems as a new concept of a chaotic dynamical system (X , T) given by a compact metric space X and a continuous surjective self-map T : X → X. Observe that each weakly mixing system is transitive compact, and we show that any transitive compact M-system is weakly mixing. Then we discuss the relationships between it and other several stronger forms of sensitivity. We prove that any transitive compact system is Li-Yorke sensitive and furthermore multi-sensitive if it is not proximal, and that any multi-sensitive system has positive topological sequence entropy. Moreover, we show that multi-sensitivity is equivalent to both thick sensitivity and thickly syndetic sensitivity for M-systems. We also give a quantitative analysis for multi-sensitivity of a dynamical system.

  9. HUBBLE SPACE TELESCOPE WFC3 GRISM SPECTROSCOPY AND IMAGING OF A GROWING COMPACT GALAXY AT z = 1.9

    SciTech Connect

    Van Dokkum, Pieter G.; Brammer, Gabriel

    2010-08-01

    We present HST/WFC3 grism near-IR spectroscopy of the brightest galaxy at z > 1.5 in the GOODS-South WFC3 ERS grism pointing. The spectrum is of remarkable quality and shows the redshifted Balmer lines H{beta}, H{gamma}, and H{delta} in absorption at z = 1.902 {+-} 0.002. The absorption lines can be produced by a post-starburst stellar population with a luminosity-weighted age of {approx}0.5 Gyr. The mass-to-light ratio inferred from the spectrum implies a stellar mass of (4 {+-} 1) x 10{sup 11} M{sub sun}. We determine the morphology of the galaxy from a deep WFC3 H{sub 160} image. Similar to other massive galaxies at z {approx} 2 the galaxy is compact, with an effective radius of 2.1 {+-} 0.3 kpc. Although most of the light is in a compact core, the galaxy has two red, smooth spiral arms that appear to be tidally induced. The spatially resolved spectroscopy demonstrates that the center of the galaxy is quiescent whereas the surrounding disk is forming stars, as it shows H{beta} in emission. The galaxy interacts with a companion at a projected distance of 18 kpc, which also shows prominent tidal features. The companion is a factor of {approx}10 fainter than the primary galaxy and may have a lower metallicity. It is tempting to interpret these observations as evidence for the growth of compact, quiescent high-redshift galaxies through minor mergers, which has been proposed by several recent observational and theoretical studies. Interestingly both objects host luminous active galactic nuclei, which implies that these mergers can be accompanied by significant black hole growth.

  10. LETTER TO THE EDITOR: Landau levels on the hyperbolic plane

    NASA Astrophysics Data System (ADS)

    Fakhri, H.; Shariati, M.

    2004-11-01

    The quantum states of a spinless charged particle on a hyperbolic plane in the presence of a uniform magnetic field with a generalized quantization condition are proved to be the bases of the irreducible Hilbert representation spaces of the Lie algebra u(1, 1). The dynamical symmetry group U(1, 1) with the explicit form of the Lie algebra generators is extracted. It is also shown that the energy has an infinite-fold degeneracy in each of the representation spaces which are allocated to the different values of the magnetic field strength. Based on the simultaneous shift of two parameters, it is also noted that the quantum states realize the representations of Lie algebra u(2) by shifting the magnetic field strength.

  11. Optical pulling forces in hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Shalin, Alexander S.; Sukhov, Sergey V.; Bogdanov, Andrey A.; Belov, Pavel A.; Ginzburg, Pavel

    2015-06-01

    Control over mechanical motion of nanoscale particles is a valuable functionality desired in a variety of multidisciplinary applications, e.g., biophysics, and it is usually achieved by employing optical forces. Hyperbolic metamaterials enable tailoring and enhancing electromagnetic scattering and, as the result, provide a platform for a new type of optical manipulation. Here optical pulling forces acting on a small particle placed inside a hyperbolic metamaterial slab were predicted and analyzed. In order to attract particles to a light source, highly confined extraordinary modes of hyperbolic metamaterial were excited via scattering from an imperfection situated at the slab's interface. This type of structured illumination together with remarkable scattering properties, inspired by the hyperbolic dispersion in the metamaterial, creates optical attraction. Forces acting on high-, low-index dielectric, and gold particles were investigated and it was shown that the pulling effect emerges in all of the cases. The ability to control mechanical motion at nanoscale using auxiliary photonic structures paves the way for investigation of various phenomena, e.g., biochemical reactions, molecular dynamics, and more.

  12. Fibonacci words, hyperbolic tilings and grossone

    NASA Astrophysics Data System (ADS)

    Margenstern, Maurice

    2015-04-01

    In this paper, we study the contribution of the theory of grossone to the study of infinite Fibonacci words, combining this tool with the help of a particular tiling of the hyperbolic plane: the tiling { 7, 3 } , called the heptagrid. With the help of the numeral system based on grossone, we obtain a richer family of infinite Fibonacci words compared with the traditional approach.

  13. Twist transition of nematic hyperbolic hedgehogs

    NASA Astrophysics Data System (ADS)

    James, Richard; Fukuda, Jun-ichi

    2014-04-01

    Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999), 10.1080/026782999204840], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell.

  14. On a microscopic representation of space-time

    SciTech Connect

    Dahm, R.

    2012-10-15

    We start from a noncompact Lie algebra isomorphic to the Dirac algebra and relate this Lie algebra in a brief review to low-energy hadron physics described by the compact group SU(4). This step permits an overall physical identification of the operator actions. Then we discuss the geometrical origin of this noncompact Lie algebra and 'reduce' the geometry in order to introduce in each of these steps coordinate definitions which can be related to an algebraic representation in terms of the spontaneous symmetry breakdown along the Lie algebra chain su*(4) {yields} usp(4) {yields} su(2) Multiplication-Sign u(1). Standard techniques of Lie algebra decomposition(s) as well as the (physical) operator identification give rise to interesting physical aspects and lead to a rank-1 Riemannian space which provides an analytic representation and leads to a 5-dimensional hyperbolic space H{sub 5} with SO(5, 1) isometries. The action of the (compact) symplectic group decomposes this (globally) hyperbolic space into H{sub 2} Circled-Plus H{sub 3} with SO(2, 1) and SO(3, 1) isometries, respectively, which we relate to electromagnetic (dynamically broken SU(2) isospin) and Lorentz transformations. Last not least, we attribute this symmetry pattern to the algebraic representation of a projective geometry over the division algebra H and subsequent coordinate restrictions.

  15. A generalized scheme for three-dimensional hyperbolic grid generation

    NASA Technical Reports Server (NTRS)

    Chan, William M.; Steger, Joseph L.

    1991-01-01

    A hyperbolic grid generation scheme formulated from grid orthogonality and cell volume specification is generalized such that high quality three-dimensional grids can be obtained for a wide variety of geometries. The speed of the scheme is one to two orders of magnitude faster than typical elliptic grid generation methods. The robustness of the scheme is significantly enhanced by several new techniques. By using a spatially variable smoothing coefficient, orthogonality and smoothness of the grid are maintained around complex concave and convex surface topologies. A metric correction procedure is employed to guarantee that the grid marches out of a corner by bisecting the angles subtended by the neighboring points. Extra robustness at severe convex corners is achieved by special local treatments. Different extrapolation methods are used to provide smoothness at floating edges and axis regions. The versatility of the new hyperbolic grid generation scheme is demonstrated by three-dimensional grids generated for external components of the intergrated Space Shuttle vehicle and the SOFIA telescope.

  16. Assimilating compact phase space retrievals of atmospheric composition with WRF-Chem/DART: a regional chemical transport/ensemble Kalman filter data assimilation system

    NASA Astrophysics Data System (ADS)

    Mizzi, Arthur P.; Arellano, Avelino F., Jr.; Edwards, David P.; Anderson, Jeffrey L.; Pfister, Gabriele G.

    2016-03-01

    This paper introduces the Weather Research and Forecasting Model with chemistry/Data Assimilation Research Testbed (WRF-Chem/DART) chemical transport forecasting/data assimilation system together with the assimilation of compact phase space retrievals of satellite-derived atmospheric composition products. WRF-Chem is a state-of-the-art chemical transport model. DART is a flexible software environment for researching ensemble data assimilation with different assimilation and forecast model options. DART's primary assimilation tool is the ensemble adjustment Kalman filter. WRF-Chem/DART is applied to the assimilation of Terra/Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) trace gas retrieval profiles. Those CO observations are first assimilated as quasi-optimal retrievals (QORs). Our results show that assimilation of the CO retrievals (i) reduced WRF-Chem's CO bias in retrieval and state space, and (ii) improved the CO forecast skill by reducing the Root Mean Square Error (RMSE) and increasing the Coefficient of Determination (R2). Those CO forecast improvements were significant at the 95 % level. Trace gas retrieval data sets contain (i) large amounts of data with limited information content per observation, (ii) error covariance cross-correlations, and (iii) contributions from the retrieval prior profile that should be removed before assimilation. Those characteristics present challenges to the assimilation of retrievals. This paper addresses those challenges by introducing the assimilation of compact phase space retrievals (CPSRs). CPSRs are obtained by preprocessing retrieval data sets with an algorithm that (i) compresses the retrieval data, (ii) diagonalizes the error covariance, and (iii) removes the retrieval prior profile contribution. Most modern ensemble assimilation algorithms can efficiently assimilate CPSRs. Our results show that assimilation of MOPITT CO CPSRs reduced the number of observations (and assimilation computation

  17. Assimilating compact phase space retrievals of atmospheric composition with WRF-Chem/DART: a regional chemical transport/ensemble Kalman filter data assimilation system

    NASA Astrophysics Data System (ADS)

    Mizzi, A. P.; Arellano, A. F.; Edwards, D. P.; Anderson, J. L.; Pfister, G. G.

    2015-09-01

    This paper introduces the Weather Research and Forecasting Model with chemistry/Data Assimilation Research Testbed (WRF-Chem/DART) chemical transport forecasting/data assimilation system together with the assimilation of "compact phase space retrievals" of satellite-derived atmospheric composition products. WRF-Chem is a state-of-the-art chemical transport model. DART is a flexible software environment for researching ensemble data assimilation with different assimilation and forecast model options. DART's primary assimilation tool is the ensemble adjustment Kalman filter. WRF-Chem/DART is applied to the assimilation of Terra/Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) trace gas retrieval profiles. Those CO observations are first assimilated as quasi-optimal retrievals (QORs). Our results show that assimilation of the CO retrievals: (i) reduced WRF-Chem's CO bias in retrieval and state space, and (ii) improved the CO forecast skill by reducing the Root Mean Square Error (RMSE) and increasing the Coefficient of Determination (R2). Those CO forecast improvements were significant at the 95 % level. Trace gas retrieval data sets contain: (i) large amounts of data with limited information content per observation, (ii) error covariance cross-correlations, and (iii) contributions from the retrieval prior profile that should be removed before assimilation. Those characteristics present challenges to the assimilation of retrievals. This paper addresses those challenges by introducing the assimilation of "compact phase space retrievals" (CPSRs). CPSRs are obtained by preprocessing retrieval datasets with an algorithm that: (i) compresses the retrieval data, (ii) diagonalizes the error covariance, and (iii) removes the retrieval prior profile contribution. Most modern ensemble assimilation algorithms can efficiently assimilate CPSRs. Our results show that assimilation of MOPITT CO CPSRs reduced the number of observations (and assimilation

  18. Feasibility study for measurement of insulation compaction in the cryogenic rocket fuel storage tanks at Kennedy Space Center by fast/thermal neutron techniques

    SciTech Connect

    Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.; Arens, E. E.

    2014-02-18

    The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and through the entire 120 cm thick perlite zone. Neutrons interactions with materials produce characteristic gamma rays which are then detected. In compacted perlite the count rates in the individual peaks in the gamma ray spectrum will increase. Portable neutron generators can produce neutron simultaneous fluxes in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scattering which is sensitive to Si, Al, Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA), which is sensitive to Si, Al, Na, K and H among others. The results of computer simulations using the software MCNP and measurements on a test article suggest that the most promising approach would be to operate the system in time-of-flight mode by pulsing the neutron generator and observing the subsequent die away curve in the PGNA signal.

  19. Feasibility study for measurement of insulation compaction in the cryogenic rocket fuel storage tanks at Kennedy Space Center by fast/thermal neutron techniques

    NASA Astrophysics Data System (ADS)

    Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.; Arens, E. E.

    2014-02-01

    The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and through the entire 120 cm thick perlite zone. Neutrons interactions with materials produce characteristic gamma rays which are then detected. In compacted perlite the count rates in the individual peaks in the gamma ray spectrum will increase. Portable neutron generators can produce neutron simultaneous fluxes in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scattering which is sensitive to Si, Al, Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA), which is sensitive to Si, Al, Na, K and H among others. The results of computer simulations using the software MCNP and measurements on a test article suggest that the most promising approach would be to operate the system in time-of-flight mode by pulsing the neutron generator and observing the subsequent die away curve in the PGNA signal.

  20. Normal hyperbolicity and unbounded critical manifolds

    NASA Astrophysics Data System (ADS)

    Kuehn, Christian

    2014-06-01

    This work is motivated by mathematical questions arising in differential equation models for autocatalytic reactions. We extend the local theory of singularities in fast-slow polynomial vector fields to classes of unbounded manifolds which lose normal hyperbolicity due to an alignment of the tangent and normal bundles. A projective transformation is used to localize the unbounded problem. Then the blow-up method is employed to characterize the loss of normal hyperbolicity for the transformed slow manifolds. Our analysis yields a rigorous scaling law for all unbounded manifolds which exhibit a power-law decay for the alignment with a fast subsystem domain. Furthermore, the proof also provides a technical extension of the blow-up method itself by augmenting the analysis with an optimality criterion for the blow-up exponents.

  1. Tunable VO2/Au hyperbolic metamaterial

    NASA Astrophysics Data System (ADS)

    Prayakarao, S.; Mendoza, B.; Devine, A.; Kyaw, C.; van Dover, R. B.; Liberman, V.; Noginov, M. A.

    2016-08-01

    Vanadium dioxide (VO2) is known to have a semiconductor-to-metal phase transition at ˜68 °C. Therefore, it can be used as a tunable component of an active metamaterial. The lamellar metamaterial studied in this work is composed of subwavelength VO2 and Au layers and is designed to undergo a temperature controlled transition from the optical hyperbolic phase to the metallic phase. VO2 films and VO2/Au lamellar metamaterial stacks have been fabricated and studied in electrical conductivity and optical (transmission and reflection) experiments. The observed temperature-dependent changes in the reflection and transmission spectra of the metamaterials and VO2 thin films are in a good qualitative agreement with theoretical predictions. The demonstrated optical hyperbolic-to-metallic phase transition is a unique physical phenomenon with the potential to enable advanced control of light-matter interactions.

  2. VIBRATION COMPACTION

    DOEpatents

    Hauth, J.J.

    1962-07-01

    A method of compacting a powder in a metal container is described including the steps of vibrating the container at above and below the resonant frequency and also sweeping the frequency of vibration across the resonant frequency several times thereby following the change in resonant frequency caused by compaction of the powder. (AEC)

  3. Hyperbolic conservation laws and numerical methods

    NASA Technical Reports Server (NTRS)

    Leveque, Randall J.

    1990-01-01

    The mathematical structure of hyperbolic systems and the scalar equation case of conservation laws are discussed. Linear, nonlinear systems and the Riemann problem for the Euler equations are also studied. The numerical methods for conservation laws are presented in a nonstandard manner which leads to large time steps generalizations and computations on irregular grids. The solution of conservation laws with stiff source terms is examined.

  4. High resolution schemes for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Harten, A.

    1983-01-01

    A class of new explicit second order accurate finite difference schemes for the computation of weak solutions of hyperbolic conservation laws is presented. These highly nonlinear schemes are obtained by applying a nonoscillatory first order accurate scheme to an appropriately modified flux function. The so-derived second order accurate schemes achieve high resolution while preserving the robustness of the original nonoscillatory first order accurate scheme. Numerical experiments are presented to demonstrate the performance of these new schemes.

  5. Hybrid surface phononic waveguide using hyperbolic boron nitride.

    PubMed

    Xu, Yuancheng; Premkumar, Navaneeth; Yang, Yuchen; Lail, Brian A

    2016-07-25

    Sub-diffraction limited waveguides have been studied as a means to manipulate light into nanoscale regions. Hybrid waveguides are popular candidates in optical regimes for subwavelength confinement and long range propagation. However, advances in the mid-IR are lacking due to high propagation losses and limited confinement. Here we present the first analysis of hybrid phononic waveguide using a hyperbolic material h-BN to generate surface phonon polaritons. The strong coupling between the photonic cylinder and phononic surface enhances the confined field up to 10-3 λo 2o is free-space wavelength) and enables propagation distances up to 100 λo. Our work is fully compatible with integrated polaritonic devices in the mid-IR and provides a systematic approach to design hybrid phononic waveguides. PMID:27464168

  6. Enhancing spontaneous emission rates of molecules using nanopatterned multilayer hyperbolic metamaterials.

    PubMed

    Lu, Dylan; Kan, Jimmy J; Fullerton, Eric E; Liu, Zhaowei

    2014-01-01

    Plasmonic nanostructures have been extensively used to manipulate the spontaneous light emission rate of molecules and their radiative efficiency. Because molecules near a metallic surface experience a different environment than in free space, their spontaneous radiative emission rate is generally enhanced. Such enhancement, measured by means of the Purcell factor, arises as a consequence of the overlap between the surface plasmon mode frequency and the emission spectrum of the molecule. However, such overlap is available only for a few narrow bands of frequency due to the limited plasmonic materials existing in nature. Although this limitation can be overcome by using hyperbolic metamaterials (HMMs)—a type of nanoscale artificial material with hyperbolic dispersion relations—the Purcell factor and the radiative power have remained relatively low. Here, we show that by nanopatterning a hyperbolic metamaterial made of Ag and Si multilayers, the spontaneous emission rate of rhodamine dye molecules is enhanced 76-fold at tunable frequencies and the emission intensity of the dye increases by ~80-fold compared with the same hyperbolic metamaterial without nanostructuring. We explain these results using a dynamic Lorentzian model in the time domain. PMID:24390565

  7. Enhancing spontaneous emission rates of molecules using nanopatterned multilayer hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Lu, Dylan; Kan, Jimmy J.; Fullerton, Eric E.; Liu, Zhaowei

    2014-01-01

    Plasmonic nanostructures have been extensively used to manipulate the spontaneous light emission rate of molecules and their radiative efficiency. Because molecules near a metallic surface experience a different environment than in free space, their spontaneous radiative emission rate is generally enhanced. Such enhancement, measured by means of the Purcell factor, arises as a consequence of the overlap between the surface plasmon mode frequency and the emission spectrum of the molecule. However, such overlap is available only for a few narrow bands of frequency due to the limited plasmonic materials existing in nature. Although this limitation can be overcome by using hyperbolic metamaterials (HMMs)--a type of nanoscale artificial material with hyperbolic dispersion relations--the Purcell factor and the radiative power have remained relatively low. Here, we show that by nanopatterning a hyperbolic metamaterial made of Ag and Si multilayers, the spontaneous emission rate of rhodamine dye molecules is enhanced 76-fold at tunable frequencies and the emission intensity of the dye increases by ~80-fold compared with the same hyperbolic metamaterial without nanostructuring. We explain these results using a dynamic Lorentzian model in the time domain.

  8. On the coupling of hyperbolic and parabolic systems: Analytical and numerical approach

    NASA Technical Reports Server (NTRS)

    Gastaldi, Fabio; Quarteroni, Alfio

    1988-01-01

    The coupling of hyperbolic and parabolic systems is discussed in a domain Omega divided into two distinct subdomains omega(+) and omega(-). The main concern is to find the proper interface conditions to be fulfilled at the surface separating the two domains. Next, they are used in the numerical approximation of the problem. The justification of the interface conditions is based on a singular perturbation analysis, i.e., the hyperbolic system is rendered parabolic by adding a small artifical viscosity. As this goes to zero, the coupled parabolic-parabolic problem degenerates into the original one, yielding some conditions at the interface. These are taken as interface conditions for the hyperbolic-parabolic problem. Actually, two alternative sets of interface conditions are discussed according to whether the regularization procedure is variational or nonvariational. It is shown how these conditions can be used in the frame of a numerical approximation to the given problem. Furthermore, a method of resolution is discussed which alternates the resolution of the hyperbolic problem within omega(-) and of the parabolic one within omega(+). The spectral collocation method is proposed, as an example of space discretization (different methods could be used as well); both explicit and implicit time-advancing schemes are considered. The present study is a preliminary step toward the analysis of the coupling between Euler and Navier-Stokes equations for compressible flows.

  9. Compact, High Energy 2-micron Coherent Doppler Wind Lidar Development for NASA's Future 3-D Winds Measurement from Space

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Koch, Grady; Yu, Jirong; Petros, Mulugeta; Beyon, Jeffrey; Kavaya, Michael J.; Trieu, Bo; Chen, Songsheng; Bai, Yingxin; Petzar, paul; Modlin, Edward A.; Barnes, Bruce W.; Demoz, Belay B.

    2010-01-01

    This paper presents an overview of 2-micron laser transmitter development at NASA Langley Research Center for coherent-detection lidar profiling of winds. The novel high-energy, 2-micron, Ho:Tm:LuLiF laser technology developed at NASA Langley was employed to study laser technology currently envisioned by NASA for future global coherent Doppler lidar winds measurement. The 250 mJ, 10 Hz laser was designed as an integral part of a compact lidar transceiver developed for future aircraft flight. Ground-based wind profiles made with this transceiver will be presented. NASA Langley is currently funded to build complete Doppler lidar systems using this transceiver for the DC-8 aircraft in autonomous operation. Recently, LaRC 2-micron coherent Doppler wind lidar system was selected to contribute to the NASA Science Mission Directorate (SMD) Earth Science Division (ESD) hurricane field experiment in 2010 titled Genesis and Rapid Intensification Processes (GRIP). The Doppler lidar system will measure vertical profiles of horizontal vector winds from the DC-8 aircraft using NASA Langley s existing 2-micron, pulsed, coherent detection, Doppler wind lidar system that is ready for DC-8 integration. The measurements will typically extend from the DC-8 to the earth s surface. They will be highly accurate in both wind magnitude and direction. Displays of the data will be provided in real time on the DC-8. The pulsed Doppler wind lidar of NASA Langley Research Center is much more powerful than past Doppler lidars. The operating range, accuracy, range resolution, and time resolution will be unprecedented. We expect the data to play a key role, combined with the other sensors, in improving understanding and predictive algorithms for hurricane strength and track. 1

  10. A hyperbolic model for viscous Newtonian flows

    NASA Astrophysics Data System (ADS)

    Peshkov, Ilya; Romenski, Evgeniy

    2016-03-01

    We discuss a pure hyperbolic alternative to the Navier-Stokes equations, which are of parabolic type. As a result of the substitution of the concept of the viscosity coefficient by a microphysics-based temporal characteristic, particle settled life (PSL) time, it becomes possible to formulate a model for viscous fluids in a form of first-order hyperbolic partial differential equations. Moreover, the concept of PSL time allows the use of the same model for flows of viscous fluids (Newtonian or non-Newtonian) as well as irreversible deformation of solids. In the theory presented, a continuum is interpreted as a system of material particles connected by bonds; the internal resistance to flow is interpreted as elastic stretching of the particle bonds; and a flow is a result of bond destructions and rearrangements of particles. Finally, we examine the model for simple shear flows, arbitrary incompressible and compressible flows of Newtonian fluids and demonstrate that Newton's viscous law can be obtained in the framework of the developed hyperbolic theory as a steady-state limit. A basic relation between the viscosity coefficient, PSL time, and the shear sound velocity is also obtained.

  11. Classical and quantum optics of hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Jacob, Zubin

    Nanotechnology has paved the way for artificial materials which have electromagnetic, mechanical, thermal and acoustic properties beyond those which are ordinarily found in nature. Photonic nanomaterials hold the promise:- to usher in a new generation of photonic devices with imaging capabilities well beyond the reach of conventional optics, to drive CMOS compatible nanophotonics research for sustaining Moores law and even address pressing societal needs of solar energy harvesting. The central theme of this thesis is the understanding of the essential physics for new devices based on nanofabricated metamaterials, where the bulk macroscopic material properties are governed and tailored at will, according to the constituent nanostructured building blocks. The particular class of metamaterials considered are uniaxial media with an extreme dielectric anisotropy i.e. materials with dielectric constants of opposite signs in the dielectric tensor. This gives rise to a hyperbolic dispersion relation for extraordinary propagating waves in the medium. We unravel a unique singularity in the photonic density of states (PDOS) of such hyperbolic metamaterials. The remarkable property which sets it apart from other photonic systems is the broad spectral bandwidth in which the PDOS diverges, paving the way for a new approach to controlling broadband light-matter interaction. We use the unique electromagnetic metamaterial states that cause the divergence in the PDOS for two specific device applications: subdiffraction imaging and quantum optics. We solve the long standing problem of the fundamental diffraction limit which plagues all conventional optical imaging systems using a device called the hyperlens, comprising of nanostructured hyperbolic metamaterials. The hyperlens produces magnified images of subwavelength objects in the far-field, promising to revolutionize applications such as nano-bio imaging and subdiffraction lithography. We show that the hyperlens can be understood

  12. Flow tests of a single fuel element coolant channel for a compact fast reactor for space power

    NASA Technical Reports Server (NTRS)

    Springborn, R. H.

    1971-01-01

    Water flow tests were conducted on a single-fuel-element cooling channel for a nuclear concept to be used for space power. The tests established a method for measuring coolant flow rate which is applicable to water flow testing of a complete mockup of the reference reactor. The inlet plenum-to-outlet plenum pressure drop, which approximates the overall core pressure drop, was measured and correlated with flow rate. This information can be used for reactor coolant flow and heat transfer calculations. An analytical study of the flow characteristics was also conducted.

  13. Embedding of simply laced hyperbolic Kac-Moody superalgebras

    NASA Astrophysics Data System (ADS)

    Nayak, Saudamini; Pati, K. C.

    2013-03-01

    We show that HD(4, 1) hyperbolic Kac-Moody superalgebra of rank 6 contains every simply laced Kac-Moody superalgebra with degenerate odd root as a Lie subalgebra. Our result is the supersymmetric extension of earlier work [S. Viswanath, "Embeddings of HyperbolicKac-Moody Algebras into E10," Lett. Math. Phys. 83, 139-148 (2008)], 10.1007/s11005-007-0214-7 for hyperbolic Kac-Moody algebra.

  14. Meta-Optics with Nanowire Grid Arrays: Hyperbolic Fabry-Perot Modes and Hyperbolic Tamm Plasmons

    NASA Astrophysics Data System (ADS)

    Durach, Maxim; Keene, David; Lepain, Matthew

    2015-03-01

    In this talk we introduce a new class of structures - cavities formed by metal-dielectric metasurfaces. These cavities support a zoo of various resonances, including hyperbolic Tamm plasmons and hyperbolic Fabry-Perot modes, which feature anisotropic clover-leaf dispersion parallel to the metasurface and strong coupling between TM and TE polarizations in the modes. The properties and spectrum of the modes are highly tunable by the dimensional and material parameters of the structure and can be used for directional emission, modification of radiation produced by electric dipole emitters into magnetic dipole radiation as well as 90 degree polarization rotators and polarization rotation mirrors.

  15. Compact Reactor

    SciTech Connect

    Williams, Pharis E.

    2007-01-30

    Weyl's Gauge Principle of 1929 has been used to establish Weyl's Quantum Principle (WQP) that requires that the Weyl scale factor should be unity. It has been shown that the WQP requires the following: quantum mechanics must be used to determine system states; the electrostatic potential must be non-singular and quantified; interactions between particles with different electric charges (i.e. electron and proton) do not obey Newton's Third Law at sub-nuclear separations, and nuclear particles may be much different than expected using the standard model. The above WQP requirements lead to a potential fusion reactor wherein deuterium nuclei are preferentially fused into helium nuclei. Because the deuterium nuclei are preferentially fused into helium nuclei at temperatures and energies lower than specified by the standard model there is no harmful radiation as a byproduct of this fusion process. Therefore, a reactor using this reaction does not need any shielding to contain such radiation. The energy released from each reaction and the absence of shielding makes the deuterium-plus-deuterium-to-helium (DDH) reactor very compact when compared to other reactors, both fission and fusion types. Moreover, the potential energy output per reactor weight and the absence of harmful radiation makes the DDH reactor an ideal candidate for space power. The logic is summarized by which the WQP requires the above conditions that make the prediction of DDH possible. The details of the DDH reaction will be presented along with the specifics of why the DDH reactor may be made to cause two deuterium nuclei to preferentially fuse to a helium nucleus. The presentation will also indicate the calculations needed to predict the reactor temperature as a function of fuel loading, reactor size, and desired output and will include the progress achieved to date.

  16. Manipulating light polarizations with a hyperbolic metamaterial waveguide.

    PubMed

    Zhu, Hua; Yin, Xiang; Chen, Lin; Zhu, Zhongshu; Li, Xun

    2015-10-15

    In this Letter we demonstrate that a hyperbolic metamaterial (HMM) waveguide array exhibits a giant modal birefringence between the TE and TM modes by utilization of a rectangular waveguide cross section. We further reveal that the designed polarization manipulation device using such a HMM waveguide array with a subwavelength thickness presents the ability to function as a polarizer or quarter- or half-wave plate that enables transmission only for electromagnetic wave (EW) that is polarized at a specific direction, or converting linearly polarized EW to circularly and elliptically polarized EW or rotating linearly polarized EW with 90° at terahertz (THz) frequencies. A giant modal birefringence between the TE and TM modes from 0.8 to 2 between 2 and 4.8 THz is achievable, which is dozens of times higher than conventional quartz birefringent crystals for THz waves. This polarization manipulation device has the performance merits including high transmission efficiency, ultra-compactness, and tunable birefringence, offering a promising approach to manipulating the polarization states of EW. PMID:26469572

  17. COMPACT SCHOOL AND $$ SAVINGS.

    ERIC Educational Resources Information Center

    BAIR, W.G.

    A REVIEW OF THE CRITERIA FOR CONSIDERING THE USE OF A TOTAL ENERGY SYSTEM WITHIN A SCHOOL BUILDING STATES THE WINDOWLESS, COMPACT SCHOOL OFFERS MORE EFFICIENT SPACE UTILIZATION WITH LESS AREA REQUIRED FOR GIVEN STUDENT POPULATION AND LOWER OPERATION COSTS. THE AUTHOR RECOMMENDS THAT THESE BUILDINGS BE WINDOWLESS TO REDUCE HEAT COSTS, HOWEVER, AT…

  18. Stability of Hyperbolic Imbeddedness and Construction of Examples

    NASA Astrophysics Data System (ADS)

    Zaĭdenberg, M. G.

    1989-02-01

    Methods are worked out for constructing smooth hyperbolic curves \\Gamma\\subset\\mathbf{CP}^2 and surfaces H\\subset\\mathbf{CP}^3 with hyperbolically imbedded complements, and the methods are then used to construct examples of such curves with least possible degree 5. The existence of these curves agrees well with the 1970 conjecture of Kobayashi. It is proved that the sets of such curves and surfaces are open (in the classical topology). The proofs are based on tests obtained for stability of hyperbolicity and of hyperbolic imbeddedness of analytic subsets of complex manifolds under perturbations that can in general reconstruct the topology.Bibliography: 18 titles.

  19. Hyperbolic Rendezvous at Mars: Risk Assessments and Mitigation Strategies

    NASA Technical Reports Server (NTRS)

    Jedrey, Ricky; Landau, Damon; Whitley, Ryan

    2015-01-01

    Given the current interest in the use of flyby trajectories for human Mars exploration, a key requirement is the capability to execute hyperbolic rendezvous. Hyperbolic rendezvous is used to transport crew from a Mars centered orbit, to a transiting Earth bound habitat that does a flyby. Representative cases are taken from future potential missions of this type, and a thorough sensitivity analysis of the hyperbolic rendezvous phase is performed. This includes early engine cutoff, missed burn times, and burn misalignment. A finite burn engine model is applied that assumes the hyperbolic rendezvous phase is done with at least two burns.

  20. On a Non-Reflecting Boundary Condition for Hyperbolic Conservation Laws

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.

    2003-01-01

    A non-reflecting boundary condition (NRBC) for practical computations in fluid dynamics and aeroacoustics is presented. The technique is based on the hyperbolicity of the Euler equation system and the first principle of plane (simple) wave propagation. The NRBC is simple and effective, provided the numerical scheme maintains locally a C(sup 1) continuous solution at the boundary. Several numerical examples in ID, 2D and 3D space are illustrated to demonstrate its robustness in practical computations.

  1. On a Non-Reflecting Boundary Condition for Hyperbolic Conservation Laws

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.

    2003-01-01

    A non-reflecting boundary condition (NRBC) for practical computations in fluid dynamics and aeroacoustics is presented. The technique is based on the first principle of non-reflecting, plane wave propagation and the hyperbolicity of the Euler equation system. The NRBC is simple and effective, provided the numerical scheme maintains locally a C(sup 1) continuous solution at the boundary. Several numerical examples in 1D, 2D, and 3D space are illustrated to demonstrate its robustness in practical computations.

  2. Asymptotic profile of a parabolic-hyperbolic system with boundary effect arising from tumor angiogenesis

    NASA Astrophysics Data System (ADS)

    Mei, Ming; Peng, Hongyun; Wang, Zhi-An

    2015-11-01

    This paper concerns a parabolic-hyperbolic system on the half space R+ with boundary effect. The system is derived from a singular chemotaxis model describing the initiation of tumor angiogenesis. We show that the solution of the system subject to appropriate boundary conditions converges to a traveling wave profile as time tends to infinity if the initial data is a small perturbation around the wave which is shifted far away from the boundary but its amplitude can be arbitrarily large.

  3. Single-material semiconductor hyperbolic metamaterials.

    PubMed

    Wei, D; Harris, C; Bomberger, C C; Zhang, J; Zide, J; Law, S

    2016-04-18

    Layered semiconductor hyperbolic metamaterials for the mid-infrared are grown by molecular beam epitaxy using a single material system, doped and undoped InAs. The onset wavelength for metamaterial behavior can be tuned from 5.8μm to beyond 10μm, while the fill factor ranges from 0.25 to 0.75, resulting in designer optical behavior. The reflection and transmission behavior were studied by Fourier transform spectroscopy and modeled using effective medium theory. We also conducted a geometric optics experiment to demonstrate negative refraction of our materials. PMID:27137307

  4. Transonic potential flow in hyperbolic nozzles

    NASA Technical Reports Server (NTRS)

    Park, M.; Caughey, D. A.

    1986-01-01

    The full potential equation for the classical problem of transonic flow through a hyperbolic nozzle (with or without a shock wave) is solved in conservation form using the finite volume method of Jameson and Caughey (1977). Either a firstor a second-order numerical viscosity is added in the direction of the flow, explicitly, in conservation form. A multigrid alternating direction implicit method is used to solve the difference equations, and the results obtained are compared with analytical and numerical results from previous researches.

  5. Geometry in the large and hyperbolic chaos

    SciTech Connect

    Hasslacher, B.; Mainieri, R.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors calculated observables in strongly chaotic systems. This is difficult to do because of a lack of a workable orbit classification for such systems. This is due to global geometrical information from the original dynamical system being entangled in an unknown way throughout the orbit sequence. They used geometrical methods from modern mathematics and recent connections between global geometry and modern quantum field theory to study the natural geometrical objects belonging to hard chaos-hyperbolic manifolds.

  6. Angular distribution of emission from hyperbolic metamaterials

    PubMed Central

    Gu, Lei; Livenere, J. E.; Zhu, G.; Tumkur, T. U.; Hu, H.; Cortes, C. L.; Jacob, Z.; Prokes, S. M.; Noginov, M. A.

    2014-01-01

    We have studied angular distribution of emission of dye molecules deposited on lamellar metal/dielectric and Si/Ag nanowire based metamaterials with hyperbolic dispersion. In agreement with the theoretical prediction, the emission pattern of dye on top of lamellar metamaterial is similar to that on top of metal. At the same time, the effective medium model predicts the emission patterns of the nanowire array and the dye film deposited on glass to be nearly identical to each other. This is not the case of our experiment. We tentatively explain the nearly Lambertian (∝cosθ) angular distribution of emission of the nanowire based sample by a surface roughness. PMID:25476126

  7. A SPITZER SPACE TELESCOPE FAR-INFRARED SPECTRAL ATLAS OF COMPACT SOURCES IN THE MAGELLANIC CLOUDS. I. THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Van Loon, Jacco Th.; Oliveira, Joana M.; Gordon, Karl D.; Meixner, Margaret; Shiao, Bernie; Boyer, Martha L.; Kemper, F.; Woods, Paul M.; Tielens, A. G. G. M.; Marengo, Massimo; Indebetouw, Remy; Chen, C.-H. Rosie; Sloan, G. C.

    2010-01-15

    We present far-infrared spectra, {lambda} = 52-93 {mu}m, obtained with the Spitzer Space Telescope in the spectral energy distribution mode of its MIPS instrument, of a representative sample of the most luminous compact far-infrared sources in the Large Magellanic Cloud (LMC). These include carbon stars, OH/IR asymptotic giant branch (AGB) stars, post-AGB objects and planetary nebulae, the R CrB-type star HV 2671, the OH/IR red supergiants (RSGs) WOH G064 and IRAS 05280 - 6910, the three B[e] stars IRAS 04530 - 6916, R 66 and R 126, the Wolf-Rayet star Brey 3a, the luminous blue variable (LBV) R 71, the supernova remnant N 49, a large number of young stellar objects (YSOs), compact H II regions and molecular cores, and a background galaxy at a redshift z {approx_equal} 0.175. We use the spectra to constrain the presence and temperature of cold dust and the excitation conditions and shocks within the neutral and ionized gas, in the circumstellar environments and interfaces with the surrounding interstellar medium (ISM). First, we introduce a spectral classification scheme. Then, we measure line strengths, dust temperatures, and IR luminosities. Objects associated with star formation are readily distinguished from evolved stars by their cold dust and/or fine-structure lines. Evolved stars, including the LBV R 71, lack cold dust except in some cases where we argue that this is swept-up ISM. This leads to an estimate of the duration of the prolific dust-producing phase ('superwind') of several thousand years for both RSGs and massive AGB stars, with a similar fractional mass loss experienced despite the different masses. We tentatively detect line emission from neutral oxygen in the extreme RSG WOH G064, which suggests a large dust-free cavity with implications for wind driving. In N 49, the shock between the supernova ejecta and ISM is revealed in spectacular fashion by its strong [O I] {lambda}63 {mu}m emission and possibly water vapor; we estimate that 0.2 M {sub

  8. Methodologies to determine forces on bones and muscles of body segments during exercise, employing compact sensors suitable for use in crowded space vehicles

    NASA Technical Reports Server (NTRS)

    Figueroa, Fernando

    1994-01-01

    A complete description of an instrumented ergometer system, including the sensors, the data acquisition system, and the methodologies to calculate the kinematic parameters were initially developed at Tulane University. This work was continued by the PI at NASA Johnson Space Center, where a flight ergometer was instrumented and tested during a KC-135 Zero-Gravity flight. The sensors that form part of the system include EMG probes and accelerometers mounted on the subject using the ergometer, load cells to measure pedal forces, and encoders to measure position and orientation of the pedal (foot). Currently, data from the flight test is being analyzed and processed to calculate the kinematic parameters of the individual. The formulation developed during the initial months of the grant will be used for this purpose. The system's components are compact (all sensors are very small). A salient feature of the system and associated methodology to determine the kinematics is that although it uses accelerometers, position is not determined by integration. Position is determined by determining the angle of two frames of reference for which acceleration at one point is known in coordinates of both frames.

  9. Contact Geometry of Hyperbolic Equations of Generic Type

    NASA Astrophysics Data System (ADS)

    The, Dennis

    2008-08-01

    We study the contact geometry of scalar second order hyperbolic equations in the plane of generic type. Following a derivation of parametrized contact-invariants to distinguish Monge-Ampère (class 6-6), Goursat (class 6-7) and generic (class 7-7) hyperbolic equations, we use Cartan's equivalence method to study the generic case. An intriguing feature of this class of equations is that every generic hyperbolic equation admits at most a nine-dimensional contact symmetry algebra. The nine-dimensional bound is sharp: normal forms for the contact-equivalence classes of these maximally symmetric generic hyperbolic equations are derived and explicit symmetry algebras are presented. Moreover, these maximally symmetric equations are Darboux integrable. An enumeration of several submaximally symmetric (eight and seven-dimensional) generic hyperbolic structures is also given.

  10. Purcell effect in hyperbolic metamaterial resonators

    NASA Astrophysics Data System (ADS)

    Slobozhanyuk, Alexey P.; Ginzburg, Pavel; Powell, David A.; Iorsh, Ivan; Shalin, Alexander S.; Segovia, Paulina; Krasavin, Alexey V.; Wurtz, Gregory A.; Podolskiy, Viktor A.; Belov, Pavel A.; Zayats, Anatoly V.

    2015-11-01

    The radiation dynamics of optical emitters can be manipulated by properly designed material structures modifying local density of photonic states, a phenomenon often referred to as the Purcell effect. Plasmonic nanorod metamaterials with hyperbolic dispersion of electromagnetic modes are believed to deliver a significant Purcell enhancement with both broadband and nonresonant nature. Here, we have investigated finite-size resonators formed by nanorod metamaterials and shown that the main mechanism of the Purcell effect in such resonators originates from the supported hyperbolic modes, which stem from the interacting cylindrical surface plasmon modes of the finite number of nanorods forming the resonator. The Purcell factors delivered by these resonator modes reach several hundreds, which is up to 5 times larger than those in the ɛ-near-zero regime. It is shown that while the Purcell factor delivered by the Fabry-Pérot modes depends on the resonator size, the decay rate in the ɛ-near-zero regime is almost insensitive to geometry. The presented analysis shows a possibility to engineer emission properties in structured metamaterials, taking into account their internal composition.

  11. Super-Planckian far-zone thermal emission from asymmetric hyperbolic metamaterials

    SciTech Connect

    Nefedov, Igor S.; Melnikov, Leonid A.

    2014-10-20

    We demonstrate the production of strong directive thermal emissions in the far-field zone of asymmetric hyperbolic metamaterials (AHMs), exceeding that predicted by Planck's limit. Asymmetry is inherent to the uniaxial medium, where the optical axis is tilted with respect to medium interfaces. The use of AHMs is shown to enhance the free-space coupling efficiency of thermally radiated waves, resulting in Super-Planckian far-field thermal emission in certain directions. This effect is impossible in usual hyperbolic materials because emission of high density of states (DOS) photons into vacuum with smaller DOS is preserved by the total internal reflection. Different plasmonic metamaterials are proposed for realizing AHM media; the thermal emission from a AHM, based on a grapheme multilayer structure, is presented, as an example.

  12. Dispersionless gaps and cavity modes in photonic crystals containing hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Xue, Chun-hua; Ding, Yaqiong; Jiang, Hai-tao; Li, Yunhui; Wang, Zhan-shan; Zhang, Ye-wen; Chen, Hong

    2016-03-01

    We theoretically study dispersionless gaps and cavity modes in one-dimensional photonic crystals composed of hyperbolic metamaterials and dielectric. Bragg gaps in conventional all-dielectric photonic crystals are always dispersive because propagating phases in two kinds of dielectrics decrease with incident angle. Here, based on phase variation compensation between a hyperbolic metamaterial layer and an isotropic dielectric layer, the dispersion of the gap can be offset and thus a dispersionless gap can be realized. Moreover, the dispersionless property of such gap has a wide parameter space. The dispersionless gap can be used to realize a dispersionless cavity mode. The dispersionless gaps and cavity modes will possess significant applications for all-angle reflectors, high-Q filters excited with finite-sized sources, and nonlinear wave mixing processes.

  13. Ureilite compaction

    NASA Astrophysics Data System (ADS)

    Walker, D.; Agee, C. B.

    1988-03-01

    Ureilite meteorites show the simple mineralogy and compact recrystallized textures of adcumulate rock or melting residues. A certain amount of controversy exists about whether they are in fact adcumulate rocks or melting residues and about the nature of the precursor liquid or solid assemblage. The authors undertook a limited experimental study which made possible the evaluation of the potential of the thermal migration mechanism (diffusion on a saturation gradient) for forming ureilite-like aggregates from carbonaceous chondrite precursors. They find that the process can produce compact recrystallized aggregates of silicate crystals which do resemble the ureilities and other interstitial-liquid-free adcumulate rocks in texture.

  14. Graphene on hexagonal boron nitride as a tunable hyperbolic metamaterial

    NASA Astrophysics Data System (ADS)

    Dai, S.; Ma, Q.; Liu, M. K.; Andersen, T.; Fei, Z.; Goldflam, M. D.; Wagner, M.; Watanabe, K.; Taniguchi, T.; Thiemens, M.; Keilmann, F.; Janssen, G. C. A. M.; Zhu, S.-E.; Jarillo-Herrero, P.; Fogler, M. M.; Basov, D. N.

    2015-08-01

    Hexagonal boron nitride (h-BN) is a natural hyperbolic material, in which the dielectric constants are the same in the basal plane (ɛt ≡ ɛx = ɛy) but have opposite signs (ɛtɛz < 0) in the normal plane (ɛz). Owing to this property, finite-thickness slabs of h-BN act as multimode waveguides for the propagation of hyperbolic phonon polaritons—collective modes that originate from the coupling between photons and electric dipoles in phonons. However, control of these hyperbolic phonon polaritons modes has remained challenging, mostly because their electrodynamic properties are dictated by the crystal lattice of h-BN. Here we show, by direct nano-infrared imaging, that these hyperbolic polaritons can be effectively modulated in a van der Waals heterostructure composed of monolayer graphene on h-BN. Tunability originates from the hybridization of surface plasmon polaritons in graphene with hyperbolic phonon polaritons in h-BN, so that the eigenmodes of the graphene/h-BN heterostructure are hyperbolic plasmon-phonon polaritons. The hyperbolic plasmon-phonon polaritons in graphene/h-BN suffer little from ohmic losses, making their propagation length 1.5-2.0 times greater than that of hyperbolic phonon polaritons in h-BN. The hyperbolic plasmon-phonon polaritons possess the combined virtues of surface plasmon polaritons in graphene and hyperbolic phonon polaritons in h-BN. Therefore, graphene/h-BN can be classified as an electromagnetic metamaterial as the resulting properties of these devices are not present in its constituent elements alone.

  15. A Spitzer Space Telescope Far-infrared Spectral Atlas of Compact Sources in the Magellanic Clouds. II. The Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    van Loon, Jacco Th.; Oliveira, Joana M.; Gordon, Karl D.; Sloan, G. C.; Engelbracht, C. W.

    2010-04-01

    We present far-infrared spectra, λ = 52-93 μm, obtained with the Spitzer Space Telescope in the spectral energy distribution mode of its Multiband Imaging Photometer for Spitzer instrument, of a selection of luminous compact far-infrared sources in the Small Magellanic Cloud (SMC). These comprise nine young stellar objects (YSOs), the compact H II region N 81 and a similar object within N 84, and two red supergiants (RSGs). We use the spectra to constrain the presence and temperature of cool dust and the excitation conditions within the neutral and ionized gas, in the circumstellar environments and interfaces with the surrounding interstellar medium. We compare these results with those obtained in the Large Magellanic Cloud (LMC). The spectra of the sources in N 81 (of which we also show the Infrared Space Observatory-Long-wavelength Spectrograph spectrum between 50 and 170 μm) and N 84 both display strong [O I] λ63 μm and [O III] λ88 μm fine-structure line emission. We attribute these lines to strong shocks and photo-ionized gas, respectively, in a "champagne flow" scenario. The nitrogen content of these two H II regions is very low, definitely N(N)/N(O) < 0.04 but possibly as low as N(N)/N(O) < 0.01. Overall, the oxygen lines and dust continuum are weaker in star-forming objects in the SMC than in the LMC. We attribute this to the lower metallicity of the SMC compared to that of the LMC. While the dust mass differs in proportion to metallicity, the oxygen mass differs less; both observations can be reconciled with higher densities inside star-forming cloud cores in the SMC than in the LMC. The dust in the YSOs in the SMC is warmer (37-51 K) than in comparable objects in the LMC (32-44 K). We attribute this to the reduced shielding and reduced cooling at the low metallicity of the SMC. On the other hand, the efficiency of the photo-electric effect to heat the gas is found to be indistinguishable to that measured in the same manner in the LMC, ≈0

  16. Output Tracking for Systems with Non-Hyperbolic and Near Non-Hyperbolic Internal Dynamics: Helicopter Hover Control

    NASA Technical Reports Server (NTRS)

    Devasia, Santosh

    1996-01-01

    A technique to achieve output tracking for nonminimum phase linear systems with non-hyperbolic and near non-hyperbolic internal dynamics is presented. This approach integrates stable inversion techniques, that achieve exact-tracking, with approximation techniques, that modify the internal dynamics to achieve desirable performance. Such modification of the internal dynamics is used (1) to remove non-hyperbolicity which an obstruction to applying stable inversion techniques and (2) to reduce large pre-actuation time needed to apply stable inversion for near non-hyperbolic cases. The method is applied to an example helicopter hover control problem with near non-hyperbolic internal dynamic for illustrating the trade-off between exact tracking and reduction of pre-actuation time.

  17. Searches for hyperbolic extra dimensions at the LHC

    NASA Astrophysics Data System (ADS)

    Melbéus, Henrik; Ohlsson, Tommy

    2008-08-01

    We investigate a model of large extra dimensions where the internal space has the geometry of a hyperbolic disc. Compared with the ADD model, this model provides a more satisfactory solution to the hierarchy problem between the electroweak scale and the Planck scale, and it also avoids constraints from astrophysics. In general, a novel feature of this model is that the physical results depend on the position of the brane in the internal space, and in particular, the signal almost disappears completely if the brane is positioned at the center of the disc. Since there is no known analytic form of the Kaluza-Klein spectrum for our choice of geometry, we obtain a spectrum based on a combination of approximations and numerical computations. We study the possible signatures of our model for hadron colliders, especially the LHC, where the most important processes are the production of a graviton together with a hadronic jet or a photon. We find that the signals are similar to those of the ADD model, regarding both qualitative behavior and strength. For the case of hadronic jet production, it is possible to obtain relatively strong signals, while for the case of photon production, this is much more difficult.

  18. Time machines with the compactly determined Cauchy horizon

    NASA Astrophysics Data System (ADS)

    Krasnikov, S.

    2014-07-01

    The building of a time machine, if possible at all, requires the relevant regions of spacetime to be compact (that is, physically speaking, free from sources of unpredictability such as infinities and singularities). Motivated by this argument we consider the spacetimes with the compactly determined Cauchy horizons (CDCHs), the defining property of which is the compactness of J-(U) ¯∩J+(S0), where U is an open subset of the Cauchy horizon and S0 is a Cauchy surface of the initial globally hyperbolic region Min. The following two facts are established: (1) Min has no globally hyperbolic maximal extension. This means that, by shaping appropriately a precompact portion of a globally hyperbolic region, one can force the Universe to produce either a closed causal curve, or a quasiregular singularity, whichever it abhors less. (2) Before a CDCH is formed a null geodesic appears which infinitely approaches the horizon returning again and again in the same—arbitrarily small—region. The energy of the photon moving on such a geodesic increases with each passage, or at least falls insufficiently fast. As a result, an observer located in the mentioned region would see a bunch of photons passing through his laboratory with the arbitrarily large total energy. We speculate that this phenomenon may have observable consequences.

  19. Approximate solutions of the hyperbolic Kepler equation

    NASA Astrophysics Data System (ADS)

    Avendano, Martín; Martín-Molina, Verónica; Ortigas-Galindo, Jorge

    2015-12-01

    We provide an approximate zero widetilde{S}(g,L) for the hyperbolic Kepler's equation S-g {{arcsinh}}(S)-L=0 for gin (0,1) and Lin [0,∞ ). We prove, by using Smale's α -theory, that Newton's method starting at our approximate zero produces a sequence that converges to the actual solution S( g, L) at quadratic speed, i.e. if S_n is the value obtained after n iterations, then |S_n-S|≤ 0.5^{2^n-1}|widetilde{S}-S|. The approximate zero widetilde{S}(g,L) is a piecewise-defined function involving several linear expressions and one with cubic and square roots. In bounded regions of (0,1) × [0,∞ ) that exclude a small neighborhood of g=1, L=0, we also provide a method to construct simpler starters involving only constants.

  20. Hyperbolic Divergence Cleaning for the MHD Equations

    NASA Astrophysics Data System (ADS)

    Dedner, A.; Kemm, F.; Kröner, D.; Munz, C.-D.; Schnitzer, T.; Wesenberg, M.

    2002-01-01

    In simulations of magnetohydrodynamic (MHD) processes the violation of the divergence constraint causes severe stability problems. In this paper we develop and test a new approach to the stabilization of numerical schemes. Our technique can be easily implemented in any existing code since there is no need to modify the solver for the MHD equations. It is based on a modified system in which the divergence constraint is coupled with the conservation laws by introducing a generalized Lagrange multiplier. We suggest a formulation in which the divergence errors are transported to the domain boundaries with the maximal admissible speed and are damped at the same time. This corrected system is hyperbolic and the density, momentum, magnetic induction, and total energy density are still conserved. In comparison to results obtained without correction or with the standard “divergence source terms,” our approach seems to yield more robust schemes with significantly smaller divergence errors.

  1. Tunable hyperbolic metamaterials utilizing phase change heterostructures

    SciTech Connect

    Krishnamoorthy, Harish N. S.; Menon, Vinod M.; Zhou, You; Ramanathan, Shriram; Narimanov, Evgenii

    2014-03-24

    We present a metal-free tunable anisotropic metamaterial where the iso-frequency surface is tuned from elliptical to hyperbolic dispersion by exploiting the metal-insulator phase transition in the correlated material vanadium dioxide (VO{sub 2}). Using VO{sub 2}-TiO{sub 2} heterostructures, we demonstrate the transition in the effective dielectric constant parallel to the layers to undergo a sign change from positive to negative as the VO{sub 2} undergoes the phase transition. The possibility to tune the iso-frequency surface in real time using external perturbations such as temperature, voltage, or optical pulses creates new avenues for controlling light-matter interaction.

  2. Rainbow Trapping in Hyperbolic Metamaterial Waveguide

    PubMed Central

    Hu, Haifeng; Ji, Dengxin; Zeng, Xie; Liu, Kai; Gan, Qiaoqiang

    2013-01-01

    The recent reported trapped “rainbow” storage of light using metamaterials and plasmonic graded surface gratings has generated considerable interest for on-chip slow light. The potential for controlling the velocity of broadband light in guided photonic structures opens up tremendous opportunities to manipulate light for optical modulation, switching, communication and light-matter interactions. However, previously reported designs for rainbow trapping are generally constrained by inherent difficulties resulting in the limited experimental realization of this intriguing effect. Here we propose a hyperbolic metamaterial structure to realize a highly efficient rainbow trapping effect, which, importantly, is not limited by those severe theoretical constraints required in previously reported insulator-negative-index-insulator, insulator-metal-insulator and metal-insulator-metal waveguide tapers, and therefore representing a significant promise to realize the rainbow trapping structure practically. PMID:23409240

  3. Implicit TVD schemes for hyperbolic conservation laws in curvilinear coordinates

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Harten, A.

    1985-01-01

    The Harten (1983, 1984) total variation-diminishing (TVD) schemes, constituting a one-parameter explicit and implicit, second-order-accurate family, have the property of not generating spurious oscillations when applied to one-dimensional, nonlinear scalar hyperbolic conservation laws and constant coefficient hyperbolic systems. These methods are presently extended to the multidimensional hyperbolic conservation laws in curvilinear coordinates. Means by which to linearize the implicit operator and solution strategies, in order to improve the computation efficiency of the implicit algorithm, are discussed. Numerical experiments with steady state airfoil calculations indicate that the proposed linearized implicit TVD schemes are accurate and robust.

  4. Linear array for covariance differencing via hyperbolic singular value decomposition

    NASA Astrophysics Data System (ADS)

    Bojanczyk, A. W.; Steinhardt, A. O.

    1989-11-01

    We consider a problem pertaining to bearing estimation in unknown noise using the covariance differencing approach, and propose a linear array of processors which exhibits a linear speed-up with respect to a uniprocessor system. Our solution hinges on a new canonic matrix factorization which we term the hyperbolic singular value decomposition. The parallel algorithm for hyperbolic SVD based bearing estimation is an adaptation of a well known biorthogonalization technique developed by Hestenes. Parallel implementations of the algorithm are based on earlier works on one-sided Jacobi methods. It turns out that strategies for parallelization of Jacobi methods are equally well applicable for computing the hyperbolic singular value decomposition.

  5. Compact accelerator

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  6. Methodologies to determine forces on bones and muscles of body segments during exercise, employing compact sensors suitable for use in crowded space vehicles

    NASA Technical Reports Server (NTRS)

    Figueroa, Fernando

    1995-01-01

    Work under this grant was carried out by the author and by a graduate research assistant. An instrumented bicycle ergometer was implemented focusing on the stated objective: to estimate the forces exerted by each muscle of the feet, calf, and thigh of an individual while bicycling. The sensors used were light and compact. These were probes to measure muscle EMG activity, miniature accelerometers, miniature load sensors, and small encoders to measure angular positions of the pedal. A methodology was developed and implemented to completely describe the kinematics of the limbs using data from the sensors. This work has been published as a Master's Thesis by the Graduate student supported by the grant. The instrumented ergometer along with the sensors and instrumentation were tested during a KC-135 Zero-Gravity flight in July, 1994. A complete description of the system and the tests performed have been published as a report submitted to NASA Johnson Space Center. The data collected during the KC-135 flight is currently being processed so that a kinematic description of the bicycling experiment will be soon determined. A methodology to estimate the muscle forces has been formulated based on previous work. The methodology involves the use of optimization concepts so that the individual muscle forces that represent variables in dynamic equations of motion may be estimated. Optimization of a criteria (goal) function such as minimization of energy will be used along with constraint equations defined by rigid body equations of motion. Use of optimization principles is necessary, because the equations of motion alone constitute an indeterminate system of equations with respect to the large amount of muscle forces which constitute the variables in these equations. The number of variables is reduced somewhat by using forces measured by the load cells installed on the pedal. These load cells measure pressure and shear forces on the foot. The author and his collaborators at NASA

  7. Direct observation of ultraslow hyperbolic polariton propagation with negative phase velocity

    NASA Astrophysics Data System (ADS)

    Yoxall, Edward; Schnell, Martin; Nikitin, Alexey Y.; Txoperena, Oihana; Woessner, Achim; Lundeberg, Mark B.; Casanova, Félix; Hueso, Luis E.; Koppens, Frank H. L.; Hillenbrand, Rainer

    2015-10-01

    Polaritons with hyperbolic dispersion are key to many emerging photonic technologies, including subdiffraction imaging, sensing and spontaneous emission engineering. Fundamental to their effective application are the lifetimes of the polaritons, as well as their phase and group velocities. Here, we combine time-domain interferometry and scattering-type near-field microscopy to visualize the propagation of hyperbolic polaritons in space and time, allowing the first direct measurement of all these quantities. In particular, we study infrared phonon polaritons in a thin hexagonal boron nitride waveguide exhibiting hyperbolic dispersion and deep subwavelength-scale field confinement. Our results reveal—in a natural material—negative phase velocity paired with a remarkably slow group velocity of 0.002c and lifetimes in the picosecond range. While these findings show the polariton's potential for mediating strong light-matter interactions and negative refraction, our imaging technique paves the way to explicit nanoimaging of polariton propagation characteristics in other two-dimensional materials, metamaterials and waveguides.

  8. [The dynamics of Phanerozoic marine animal diversity agrees with the hyperbolic growth model].

    PubMed

    Markov, A V; Korotaev, A V

    2007-01-01

    Generic diversity dynamics of the Phanerozoic marine animals is far better described by the hyperbolic model, widely used in demography and macrosociology, than by the exponential and logistic models from population dynamics traditionally employed for this purpose. Exponential and logistic models imply zero influence of interactions between taxa on the dynamics of diversity, with the exception of competing for unoccupied ecological space, whereas the hyperbolic model implies non-linear second-order positive feedback in the development of the biota. The hyperbolic human population growth is caused by positive feedback between population size and the rate of technological and cultural development (the more individuals, the more inventors, the more rapid progress, the more rapid growth of the Earth's bearing capacity; the smaller death-rate, the more accelerated growth-rate of the population). Probably there is also non-linear second-order positive feedback between diversity and community structure (the more genera, the higher alpha-diversity, which is defined as average number of genera per community, the more complicated and stable, "buffered" communities, the greater "taxonomic capacity of the environment" and average duration of the existence of genera; extinction rate dencreases, biodiversity growth-rate increases). The simplest mathematical model of biodiversity dynamics based on this assumption is confirmed by empirical data on alpha-diversity dynamics. Progressive complexification of marine communities during the Phanerozoic is also confirmed by the growing evennes of generic abundance distribution in paleocommunities. PMID:17338263

  9. Bifurcation Structures in a Family of 1D Discontinuous Linear-Hyperbolic Invertible Maps

    NASA Astrophysics Data System (ADS)

    Makrooni, Roya; Gardini, Laura; Sushko, Iryna

    2015-12-01

    We consider a family of one-dimensional discontinuous invertible maps from an application in engineering. It is defined by a linear function and by a hyperbolic function with real exponent. The presence of vertical and horizontal asymptotes of the hyperbolic branch leads to particular codimension-two border collision bifurcation (BCB) such that if the parameter point approaches the bifurcation value from one side then the related cycle undergoes a regular BCB, while if the same bifurcation value is approached from the other side then a nonregular BCB occurs, involving periodic points at infinity, related to the asymptotes of the map. We investigate the bifurcation structure in the parameter space. Depending on the exponent of the hyperbolic branch, different period incrementing structures can be observed, where the boundaries of a periodicity region are related either to subcritical, or supercritical, or degenerate flip bifurcations of the related cycle, as well as to a regular or nonregular BCB. In particular, if the exponent is positive and smaller than one, then the period incrementing structure with bistability regions is observed and the corresponding flip bifurcations are subcritical, while if the exponent is larger than one, then the related flip bifurcations are supercritical and, thus, also the regions associated with cycles of double period are involved into the incrementing structure.

  10. Spinning compact binary dynamics and chameleon orbits

    NASA Astrophysics Data System (ADS)

    Gergely, László Árpád; Keresztes, Zoltán

    2015-01-01

    We analyze the conservative evolution of spinning compact binaries to second post-Newtonian (2PN) order accuracy, with leading-order spin-orbit, spin-spin and mass quadrupole-monopole contributions included. As a main result we derive a closed system of first-order differential equations in a compact form, for a set of dimensionless variables encompassing both orbital elements and spin angles. These evolutions are constrained by conservation laws holding at 2PN order. As required by the generic theory of constrained dynamical systems we perform a consistency check and prove that the constraints are preserved by the evolution. We apply the formalism to show the existence of chameleon orbits, whose local, orbital parameters evolve from elliptic (in the Newtonian sense) near pericenter, towards hyperbolic at large distances. This behavior is consistent with the picture that general relativity predicts stronger gravity at short distances than Newtonian theory does.

  11. Compaction managed mirror bend achromat

    DOEpatents

    Douglas, David

    2005-10-18

    A method for controlling the momentum compaction in a beam of charged particles. The method includes a compaction-managed mirror bend achromat (CMMBA) that provides a beamline design that retains the large momentum acceptance of a conventional mirror bend achromat. The CMMBA also provides the ability to tailor the system momentum compaction spectrum as desired for specific applications. The CMMBA enables magnetostatic management of the longitudinal phase space in Energy Recovery Linacs (ERLs) thereby alleviating the need for harmonic linearization of the RF waveform.

  12. Multidimensional explicit difference schemes for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Vanleer, B.

    1983-01-01

    First and second order explicit difference schemes are derived for a three dimensional hyperbolic system of conservation laws, without recourse to dimensional factorization. All schemes are upwind (backward) biased and optimally stable.

  13. Multidimensional explicit difference schemes for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Van Leer, B.

    1984-01-01

    First- and second-order explicit difference schemes are derived for a three-dimensional hyperbolic system of conservation laws, without recourse to dimensional factorization. All schemes are upwind biased and optimally stable.

  14. Hyperbolic metamaterials: new physics behind a classical problem.

    PubMed

    Drachev, Vladimir P; Podolskiy, Viktor A; Kildishev, Alexander V

    2013-06-17

    Hyperbolic materials enable numerous surprising applications that include far-field subwavelength imaging, nanolithography, and emission engineering. The wavevector of a plane wave in these media follows the surface of a hyperboloid in contrast to an ellipsoid for conventional anisotropic dielectric. The consequences of hyperbolic dispersion were first studied in the 50's pertaining to the problems of electromagnetic wave propagation in the Earth's ionosphere and in the stratified artificial materials of transmission lines. Recent years have brought explosive growth in optics and photonics of hyperbolic media based on metamaterials across the optical spectrum. Here we summarize earlier theories in the Clemmow's prescription for transformation of the electromagnetic field in hyperbolic media and provide a review of recent developments in this active research area. PMID:23787692

  15. Tracking discontinuities in hyperbolic conservation laws with spectral accuracy

    NASA Astrophysics Data System (ADS)

    Touil, H.; Hussaini, M. Y.; Sussman, M.

    2007-08-01

    It is well known that the spectral solutions of conservation laws have the attractive distinguishing property of infinite-order convergence (also called spectral accuracy) when they are smooth (e.g., [C. Canuto, M.Y. Hussaini, A. Quarteroni, T.A. Zang, Spectral Methods for Fluid Dynamics, Springer-Verlag, Heidelberg, 1988; J.P. Boyd, Chebyshev and Fourier Spectral Methods, second ed., Dover, New York, 2001; C. Canuto, M.Y. Hussaini, A. Quarteroni, T.A. Zang, Spectral Methods: Fundamentals in Single Domains, Springer-Verlag, Berlin Heidelberg, 2006]). If a discontinuity or a shock is present in the solution, this advantage is lost. There have been attempts to recover exponential convergence in such cases with rather limited success. The aim of this paper is to propose a discontinuous spectral element method coupled with a level set procedure, which tracks discontinuities in the solution of nonlinear hyperbolic conservation laws with spectral convergence in space. Spectral convergence is demonstrated in the case of the inviscid Burgers equation and the one-dimensional Euler equations.

  16. Soft Mappings Space

    PubMed Central

    Ozturk, Taha Yasin; Bayramov, Sadi

    2014-01-01

    Various soft topologies are being introduced on a given function space soft topological spaces. In this paper, soft compact-open topology is defined in functional spaces of soft topological spaces. Further, these functional spaces are studied and interrelations between various functional spaces with soft compact-open topology are established. PMID:25374936

  17. Compton-like polariton scattering in hyperbolic metamaterials.

    PubMed

    Iorsh, Ivan V; Poddubny, Alexander N; Ginzburg, Pavel; Belov, Pavel A; Kivshar, Yuri S

    2015-05-01

    We study the scattering of polaritons by free electrons in hyperbolic photonic media and demonstrate that the unconventional dispersion and high local density of states of electromagnetic modes in composite media with hyperbolic dispersion can lead to a giant Compton-like shift and dramatic enhancement of the scattering cross section. We develop a universal approach to study multiphoton processes in nanostructured media and derive the intensity spectrum of the scattered radiation for realistic metamaterial structures. PMID:26001008

  18. Local normal forms of smooth weakly hyperbolic integrable systems

    NASA Astrophysics Data System (ADS)

    Jiang, Kai

    2016-01-01

    In the smooth ( C∞) category, a completely integrable system near a nondegenerate singularity is geometrically linearizable if the action generated by the vector fields is weakly hyperbolic. This proves partially a conjecture of Nguyen Tien Zung [11]. The main tool used in the proof is a theorem of Marc Chaperon [3] and the slight hypothesis of weak hyperbolicity is generic when all the eigenvalues of the differentials of the vector fields at the non-degenerate singularity are real.

  19. Acceleration of reverse analysis method using hyperbolic activation function

    NASA Astrophysics Data System (ADS)

    Pwasong, Augustine; Sathasivam, Saratha

    2015-10-01

    Hyperbolic activation function is examined for its ability to accelerate the performance of doing data mining by using a technique named as Reverse Analysis method. In this paper, we describe how Hopfield network perform better with hyperbolic activation function and able to induce logical rules from large database by using reverse analysis method: given the values of the connections of a network, we can hope to know what logical rules are entrenched in the database. We limit our analysis to Horn clauses.

  20. Compact magnetograph

    NASA Technical Reports Server (NTRS)

    Title, A. M.; Gillespie, B. A.; Mosher, J. W.

    1982-01-01

    A compact magnetograph system based on solid Fabry-Perot interferometers as the spectral isolation elements was studied. The theory of operation of several Fabry-Perot systems, the suitability of various magnetic lines, signal levels expected for different modes of operation, and the optimal detector systems were investigated. The requirements that the lack of a polarization modulator placed upon the electronic signal chain was emphasized. The PLZT modulator was chosen as a satisfactory component with both high reliability and elatively low voltage requirements. Thermal control, line centering and velocity offset problems were solved by a Fabry-Perot configuration.

  1. The Luminosity, Mass, and Age Distributions of Compact Star Clusters in M83 Based on Hubble Space Telescope/Wide Field Camera 3 Observations

    NASA Astrophysics Data System (ADS)

    Chandar, Rupali; Whitmore, Bradley C.; Kim, Hwihyun; Kaleida, Catherine; Mutchler, Max; Calzetti, Daniela; Saha, Abhijit; O'Connell, Robert; Balick, Bruce; Bond, Howard; Carollo, Marcella; Disney, Michael; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick; Paresce, Francesco; Silk, Joe; Trauger, John; Walker, Alistair R.; Windhorst, Rogier A.; Young, Erick

    2010-08-01

    The newly installed Wide Field Camera 3 (WFC3) on the Hubble Space Telescope has been used to obtain multi-band images of the nearby spiral galaxy M83. These new observations are the deepest and highest resolution images ever taken of a grand-design spiral, particularly in the near-ultraviolet, and allow us to better differentiate compact star clusters from individual stars and to measure the luminosities of even faint clusters in the U band. We find that the luminosity function (LF) for clusters outside of the very crowded starburst nucleus can be approximated by a power law, dN/dL vprop L α, with α = -2.04 ± 0.08, down to MV ≈ -5.5. We test the sensitivity of the LF to different selection techniques, filters, binning, and aperture correction determinations, and find that none of these contribute significantly to uncertainties in α. We estimate ages and masses for the clusters by comparing their measured UBVI, Hα colors with predictions from single stellar population models. The age distribution of the clusters can be approximated by a power law, dN/dτ vprop τγ, with γ = -0.9 ± 0.2, for M >~ few × 103 M sun and τ <~ 4 × 108 yr. This indicates that clusters are disrupted quickly, with ≈80%-90% disrupted each decade in age over this time. The mass function of clusters over the same M-τ range is a power law, dN/dM vprop M β, with β = -1.94 ± 0.16, and does not have bends or show curvature at either high or low masses. Therefore, we do not find evidence for a physical upper mass limit, MC , or for the earlier disruption of lower mass clusters when compared with higher mass clusters, i.e., mass-dependent disruption. We briefly discuss these implications for the formation and disruption of the clusters.

  2. THE LUMINOSITY, MASS, AND AGE DISTRIBUTIONS OF COMPACT STAR CLUSTERS IN M83 BASED ON HUBBLE SPACE TELESCOPE/WIDE FIELD CAMERA 3 OBSERVATIONS

    SciTech Connect

    Chandar, Rupali; Whitmore, Bradley C.; Mutchler, Max; Bond, Howard; Kim, Hwihyun; Kaleida, Catherine; Calzetti, Daniela; Saha, Abhijit; O'Connell, Robert; Balick, Bruce; Carollo, Marcella; Disney, Michael; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick; Paresce, Francesco; Silk, Joe

    2010-08-10

    The newly installed Wide Field Camera 3 (WFC3) on the Hubble Space Telescope has been used to obtain multi-band images of the nearby spiral galaxy M83. These new observations are the deepest and highest resolution images ever taken of a grand-design spiral, particularly in the near-ultraviolet, and allow us to better differentiate compact star clusters from individual stars and to measure the luminosities of even faint clusters in the U band. We find that the luminosity function (LF) for clusters outside of the very crowded starburst nucleus can be approximated by a power law, dN/dL {proportional_to} L {sup {alpha}}, with {alpha} = -2.04 {+-} 0.08, down to M{sub V} {approx} -5.5. We test the sensitivity of the LF to different selection techniques, filters, binning, and aperture correction determinations, and find that none of these contribute significantly to uncertainties in {alpha}. We estimate ages and masses for the clusters by comparing their measured UBVI, H{alpha} colors with predictions from single stellar population models. The age distribution of the clusters can be approximated by a power law, dN/d{tau} {proportional_to} {tau}{sup {gamma}}, with {gamma} = -0.9 {+-} 0.2, for M {approx}> few x 10{sup 3} M {sub sun} and {tau} {approx}< 4 x 10{sup 8} yr. This indicates that clusters are disrupted quickly, with {approx}80%-90% disrupted each decade in age over this time. The mass function of clusters over the same M-{tau} range is a power law, dN/dM {proportional_to} M {sup {beta}}, with {beta} = -1.94 {+-} 0.16, and does not have bends or show curvature at either high or low masses. Therefore, we do not find evidence for a physical upper mass limit, M{sub C} , or for the earlier disruption of lower mass clusters when compared with higher mass clusters, i.e., mass-dependent disruption. We briefly discuss these implications for the formation and disruption of the clusters.

  3. Modeling of ultrashort pulsed laser irradiation in the cornea based on parabolic and hyperbolic heat equations using electrical analogy

    NASA Astrophysics Data System (ADS)

    Gheitaghy, A. M.; Takabi, B.; Alizadeh, M.

    2014-03-01

    Hyperbolic and parabolic heat equations are formulated to study a nonperfused homogeneous transparent cornea irradiated by high power and ultrashort pulsed laser in the Laser Thermo Keratoplasty (LTK) surgery. Energy absorption inside the cornea is modeled using the Beer-Lambert law that is incorporated as an exponentially decaying heat source. The hyperbolic and parabolic bioheat models of the tissue were solved by exploiting the mathematical analogy between thermal and electrical systems, by using robust circuit simulation program called Hspice to get the solutions of simultaneous RLC and RC transmission line networks. This method can be used to rapidly calculate the temperature in laser-irradiated tissue at time and space domain. It is found that internal energy gained from the irradiated field results in a rapid rise of temperature in the cornea surface during the early heating period, while the hyperbolic wave model predicts a higher temperature rise than the classical heat diffusion model. In addition, this paper investigates and examines the effect of some critical parameters such as relaxation time, convection coefficient, radiation, tear evaporation and variable thermal conductivity of cornea. Accordingly, it is found that a better accordance between hyperbolic and parabolic models will be achieved by time.

  4. Hyperbolic models for two-phase (or two-material) flow

    SciTech Connect

    Hicks, D.L.

    1981-08-01

    For some time it has been known that many of the two-phase flow models lead to ill-posed problems unless viscous stresses are included. The inclusion of viscous stresses changes the character of the equations from hyperbolic to parabolic. A continuing problem has been to find a well-posed hyperbolic system of equations which provide a reasonable model for two-phase flow, or to show that no such model exists. Another outstanding problem has been to understand why the derivation procedures for microstructural models produce models with the peculiar defect of being unstable. A careful investigation of the derivation procedures for the simple case of stratified flow suggests that the equal-pressures assumption is most likely the assumption leading to instability. Consideration of the alternative assumption suggests a model, namely the Unequal-Pressures Model, which is expressed by a first order system of partial differential equations with real characteristics. Thus the problem of complex characteristics (or sound speeds) which lead to the instability in the equal-pressures models is obviated. The form that the analysis takes suggests a technique for categorizing models according to the evolution equations for their internal state variables in order to aid model builders in quickly determining which models will lead to complex characteristics. Also a model with real characteristics for the two-phase flow of a bubbly liquid arises from an extension of the Unequal-Pressures model for single-layered flow to multi-layered flow. This Unequal-Pressures model has real characteristics fo all physically acceptable states and has a complete set of eigenvectors except for a set of measure zero in state space and therefore is hyperbolic in state space. Also this Unequal-Pressures model is stable in the sense of von Neumann a.e. in state space.

  5. Compact Spreader Schemes

    SciTech Connect

    Placidi, M.; Jung, J. -Y.; Ratti, A.; Sun, C.

    2014-07-25

    This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.

  6. Compact waveguide splitter networks.

    PubMed

    Qian, Yusheng; Song, Jiguo; Kim, Seunghyun; Hu, Weisheng; Nordin, Gregory P

    2008-03-31

    We demonstrate compact waveguide splitter networks in siliconon- insulator (SOI) rib waveguides using trench-based splitters (TBSs) and bends (TBBs). Rather than a 90 degrees geometry, we use 105 degrees TBSs to facilitate reliable fabrication of high aspect ratio trenches suitable for 50/50 splitting when filled with SU8. Three dimensional (3D) finite difference time domain (FDTD) simulation is used for splitter and bend design. Measured TBB and TBS optical efficiencies are 84% and 68%, respectively. Compact 105 degrees 1 x 4, 1 x 8, and 1 x 32 trench-based splitter networks (TBSNs) are demonstrated. The measured total optical loss of the 1 x 32 TBSN is 9.15 dB. Its size is only 700 microm x 1600 microm for an output waveguide spacing of 50 microm. PMID:18542598

  7. Unstaggered Central Schemes for Hyperbolic Systems

    NASA Astrophysics Data System (ADS)

    Touma, R.

    2009-09-01

    We develop an unstaggered central scheme for approximating the solution of general two-dimensional hyperbolic systems. In particular, we are interested in solving applied problems arising in hydrodynamics and astrophysics. In contrast with standard central schemes that evolve the numerical solution on two staggered grids at consecutive time steps, the method we propose evolves the numerical solution on a single grid, and avoids the resolution of the Riemann problems arising at the cell interfaces, thanks to a layer of ghost cells implicitly used. The numerical base scheme is used to solve shallow water equation problems and ideal magnetohydrodynamic problems. To satisfy the divergence-free constraint of the magnetic field in the numerical solution of ideal magnetohydrodynamic problems, we adapt Evans and Hawley's the constrained transport method to our unstaggered base scheme, and apply it to correct the magnetic field components at the end of each time step. The obtained results are in good agreement with corresponding ones appearing in the recent literature, thus confirming the efficiency and the potential of the proposed method.

  8. Multidimensional quasilinear first-order equations and multivalued solutions of the elliptic and hyperbolic equations

    NASA Astrophysics Data System (ADS)

    Zhuravlev, V. M.

    2016-03-01

    We discuss an extension of the theory of multidimensional second-order equations of the elliptic and hyperbolic types related to multidimensional quasilinear autonomous first-order partial differential equations. Calculating the general integrals of these equations allows constructing exact solutions in the form of implicit functions. We establish a connection with hydrodynamic equations. We calculate the number of free functional parameters of the constructed solutions. We especially construct and analyze implicit solutions of the Laplace and d'Alembert equations in a coordinate space of arbitrary finite dimension. In particular, we construct generalized Penrose-Rindler solutions of the d'Alembert equation in 3+1 dimensions.

  9. Numerical Algorithm Based on Haar-Sinc Collocation Method for Solving the Hyperbolic PDEs

    PubMed Central

    Javadi, H. H. S.; Navidi, H. R.

    2014-01-01

    The present study investigates the Haar-Sinc collocation method for the solution of the hyperbolic partial telegraph equations. The advantages of this technique are that not only is the convergence rate of Sinc approximation exponential but the computational speed also is high due to the use of the Haar operational matrices. This technique is used to convert the problem to the solution of linear algebraic equations via expanding the required approximation based on the elements of Sinc functions in space and Haar functions in time with unknown coefficients. To analyze the efficiency, precision, and performance of the proposed method, we presented four examples through which our claim was confirmed. PMID:25485295

  10. Triangle based adaptive stencils for the solution of hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Durlofsky, Louis J.; Engquist, Bjorn; Osher, Stanley

    1992-01-01

    A triangle based total variation diminishing (TVD) scheme for the numerical approximation of hyperbolic conservation laws in two space dimensions is constructed. The novelty of the scheme lies in the nature of the preprocessing of the cell averaged data, which is accomplished via a nearest neighbor linear interpolation followed by a slope limiting procedures. Two such limiting procedures are suggested. The resulting method is considerably more simple than other triangle based non-oscillatory approximations which, like this scheme, approximate the flux up to second order accuracy. Numerical results for linear advection and Burgers' equation are presented.

  11. Bifurcation under parameter change of Riemann solutions for nonstrictly hyperbolic systems

    NASA Astrophysics Data System (ADS)

    Matos, V.; Azevedo, A. V.; Da Mota, J. C.; Marchesin, D.

    2015-08-01

    We study the bifurcation of Riemann solutions due to parameter change that alters the type of an umbilic point existing in state space. Solutions with data near generic umbilic points are primarily determined by the local quadratic expansion of flux functions. We observe that near an umbilic point, the bifurcation of the solution is essentially local and its behavior depends solely on the cubic expansion of the flux functions. These phenomena are illustrated for immiscible three-phase flow in porous media, which looses strict hyperbolicity at an isolated point in the interior of the oil-water-gas saturation triangle.

  12. Absence of solutions of differential inequalities and systems of hyperbolic type in conic domains

    NASA Astrophysics Data System (ADS)

    Laptev, G. G.

    2002-12-01

    We establish conditions sufficient for the absence of global solutions of semilinear hyperbolic inequalities and systems in conic domains of the Euclidean space \\mathbb R^N. We consider a model problem in a cone K: that given by the inequality \\displaystyle \\dfrac{\\partial^2u}{\\partial t^2}-\\Delta u\\geqslant \\vert u\\vert^q, \\qquad (x,t)\\in K\\times(0,\\infty), The proof is based on the test-function method developed by Veron, Mitidieri, Pokhozhaev, and Tesei.

  13. Design theory of thin film hyperbolic metamaterial colimators

    NASA Astrophysics Data System (ADS)

    Fullager, Daniel B.; Fiddy, Michael A.

    2015-09-01

    Hyperbolic metamaterial (HMM) research has led to the fabrication of devices which have unbounded k-space ellipsoids. Alternating layers of films with alternating signs of relative permittivity or permeability in a given direction enable multi-layer surfaces that are, in theory, either perfectly reflective or transmissive at an angle dependent upon the free space wave vector and ratios of the permittivity or permeability in the normal and transverse directions. By having knowledge of the electromagnetic properties of the constituent materials of a multi-layer HMM over a given bandwidth, the functionality of these structures can be altered by changing the fill fraction of the constituents. One potential device design that results is that of a flat electromagnetic wave collimator. The degree to which a multi-layer HMM collimates comes from the contrast in the magnitudes of the relative permeability or permittivity in the normal and transverse directions. With a large material parameter contrast at a given frequency, the number of transverse wave vectors that allow for successful EM wave propagation at the HMM/atmosphere interface approaches zero. This leads to propagation of a narrow angular cone of waves relative to the surface normal of the HMM. Herein we show that analytical calculations are in relatively good agreement with finite element method electromagnetic simulations performed in COMSOL's RF module and compare dispersion relations of known materials to the resulting collimation generated in a corresponding HMM. We thereby use existing material data and predictive theories show how to tailor the frequency response of HMMs.

  14. Elliptical varied line-space (EVLS) gratings

    NASA Astrophysics Data System (ADS)

    Thomas, Roger J.

    2004-10-01

    Imaging spectroscopy at wavelengths below 2000 Å offers an especially powerful method for studying many extended high-temperature astronomical objects, like the Sun and its outer layers. But the technology to make such measurements is also especially challenging, because of the poor reflectance of all standard materials at these wavelengths, and because the observation must be made from above the absorbing effects of the Earth's atmosphere. To solve these problems, single-reflection stigmatic spectrographs for XUV wavelengths have bee flown on several space missions based on designs with toroidal uniform line-space (TULS) or spherical varied line-space (SVLS) gratings that operate at near normal-incidence. More recently, three solar EUV/UV instruments have been selected that use toroidal varied line-space (TVLS) gratings; these are SUMI and RAISE, both sounding rocket payloads, and NEXUS, a SMEX satellite-mission. The next logical extension to such designs is the use of elliptical surfaces for varied line-space (EVLS) rulings. In fact, EVLS designs are found to provide superior imaging even at very large spectrograph magnifications and beam-speeds, permitting extremely high-quality performance in remarkably compact instrument packages. In some cases, such designs may be optimized even further by using a hyperbolic surface for the feeding telescope. The optical characteristics of two solar EUV spectrometers based on these concepts are described: EUS and EUI, both being developed as possible instruments for ESA's Solar Orbiter mission by consortia led by RAL and by MSSL, respectively.

  15. Compact electrostatic comb actuator

    DOEpatents

    Rodgers, M. Steven; Burg, Michael S.; Jensen, Brian D.; Miller, Samuel L.; Barnes, Stephen M.

    2000-01-01

    A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

  16. Compact Q-balls

    NASA Astrophysics Data System (ADS)

    Bazeia, D.; Losano, L.; Marques, M. A.; Menezes, R.; da Rocha, R.

    2016-07-01

    In this work we deal with non-topological solutions of the Q-ball type in two space-time dimensions, in models described by a single complex scalar field that engenders global symmetry. The main novelty is the presence of stable Q-balls solutions that live in a compact interval of the real line and appear from a family of models controlled by two distinct parameters. We find analytical solutions and study their charge and energy, and show how to control the parameters to make the Q-balls classically and quantum mechanically stable.

  17. Epitaxial thin films for hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Fullager, D.; Alisafaee, H.; Tsu, R.; Fiddy, M. A.

    2014-02-01

    Recent progress in the area of hyperbolic metamaterials (HMMs) has sparked interest in transparent conducting oxides (TCOs) that behave as plasmonic media in the near-IR and at optical frequencies for imaging and sensing applications. It has been shown that by depositing alternating layers of negative-epsilon/positive-epsilon materials, a medium can be created with unusual index values such as near zero. HMMs support high-k waves corresponding to a diverging photonic density of states (PDOS), the quantity determining phenomena such as spontaneous and thermal emission. Also, modeling such structures allows evanescent fields containing sub-wavelength information to be coupled to propagating radiation. We investigate the optical, electronic, and physical properties of radio frequency plasma-assisted molecular beam epitaxial (RF-MBE) growth of alternating layers of ZnO and TCO of uniform thickness for HMM applications. Preliminary work creating HMMs with ZnO and Al-doped ZnO (AZO) has shown a negative real part of the permittivity at near-IR whose modulus is proportional to the number density of Al dopant. However, increasing the Al content of the AZO increases the transmission losses to unacceptable levels for device applications at industry standard wavelengths. A TCO with conductivity and physical structure superior to that of AZO is gallium-doped ZnO (GZO). Uniformly grown GZO has been demonstrated to possess improved crystal quality over AZO due to the higher diffusivity of Al in the ZnO. AZO and GZO HMM structures grown by RF-MBE are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Hall effect, four-point probing, deeplevel transient spectroscopy (DLTS), ellipsometry, visible and ultraviolet spectroscopy (UV-VIS) and in-situ reflection high energy electron diffraction (RHEED).

  18. Baryon currents in QCD with compact dimensions

    SciTech Connect

    Lucini, B.; Patella, A.; Pica, C.

    2007-06-15

    On a compact space with nontrivial cycles, for sufficiently small values of the radii of the compact dimensions, SU(N) gauge theories coupled with fermions in the fundamental representation spontaneously break charge conjugation, time reversal, and parity. We show at one loop in perturbation theory that a physical signature for this phenomenon is a nonzero baryonic current wrapping around the compact directions. The persistence of this current beyond the perturbative regime is checked by lattice simulations.

  19. Experimental evidence of hyperbolic heat conduction in processed meat

    SciTech Connect

    Mitra, K.; Kumar, S.; Vedavarz, A.; Moallemi, M.K.

    1995-08-01

    The objective of this paper is to present experimental evidence of the wave nature of heat propagation in processed meat and to demonstrate that the hyperbolic heat conduction model is an accurate representation, on a macroscopic level, of the heat conduction process in such biological material. The value of the characteristic thermal time of a specific material, processed bologna meat, is determined experimentally. As a part of the work different thermophysical properties are also measured. The measured temperature distributions in the samples are compared with the Fourier results and significant deviation between the two is observed, especially during the initial stages of the transient conduction process. The measured values are found to match the theoretical non-Fourier hyperbolic predictions very well. The superposition of waves occurring inside the meat sample due to the hyperbolic nature of heat conduction is also proved experimentally. 14 refs., 7 figs., 2 tabs.

  20. Bulk plasmon-polaritons in hyperbolic nanorod metamaterial waveguides

    PubMed Central

    Vasilantonakis, Nikolaos; Nasir, Mazhar E; Dickson, Wayne; Wurtz, Gregory A; Zayats, Anatoly V

    2015-01-01

    Hyperbolic metamaterials comprised of an array of plasmonic nanorods provide a unique platform for designing optical sensors and integrating nonlinear and active nanophotonic functionalities. In this work, the waveguiding properties and mode structure of planar anisotropic metamaterial waveguides are characterized experimentally and theoretically. While ordinary modes are the typical guided modes of the highly anisotropic waveguides, extraordinary modes, below the effective plasma frequency, exist in a hyperbolic metamaterial slab in the form of bulk plasmon-polaritons, in analogy to planar-cavity exciton-polaritons in semiconductors. They may have very low or negative group velocity with high effective refractive indices (up to 10) and have an unusual cut-off from the high-frequency side, providing deep-subwavelength (λ0/6–λ0/8 waveguide thickness) single-mode guiding. These properties, dictated by the hyperbolic anisotropy of the metamaterial, may be tuned by altering the geometrical parameters of the nanorod composite. PMID:26693254

  1. Vacuum in a strong magnetic field as a hyperbolic metamaterial.

    PubMed

    Smolyaninov, Igor I

    2011-12-16

    As demonstrated by Chernodub, vacuum in a strong magnetic field behaves as Abrikosov vortex lattice in a type-II superconductor. We investigate electromagnetic behavior of vacuum in this state and demonstrate that vacuum behaves as a hyperbolic metamaterial. If the magnetic field is constant, low frequency extraordinary photons experience this medium as a (3+1) Minkowski spacetime in which the role of time is played by the spatial z coordinate. Variations of the magnetic field curve this spacetime, and may lead to formation of "electromagnetic black holes." Since hyperbolic metamaterials behave as diffractionless "perfect lenses," and large enough magnetic fields probably existed in the early Universe, the demonstrated hyperbolic behavior of early vacuum may have imprints in the large scale structure of the present-day Universe. PMID:22243076

  2. Hyperbolic inflation in the light of Planck 2015 data

    NASA Astrophysics Data System (ADS)

    Basilakos, Spyros; Barrow, John D.

    2015-05-01

    Rubano and Barrow have discussed the emergence of a dark energy, with late-time cosmic acceleration arising from a self-interacting homogeneous scalar field with a potential of hyperbolic power type. Here, we study the evolution of this scalar-field potential back in the inflationary era. Using the hyperbolic power potential in the framework of inflation, we find that the main slow-roll parameters, like the scalar spectral index, the running of the spectral index and the tensor-to-scalar fluctuation ratio can be computed analytically. Finally, in order to test the viability of this hyperbolic scalar-field model at the early stages of the Universe, we compare the predictions of that model with the latest observational data, namely Planck 2015.

  3. Virtual hyperbolic metamaterials for manipulating radar signals in air

    NASA Astrophysics Data System (ADS)

    Kudyshev, Zhaxylyk A.; Richardson, Martin C.; Litchinitser, Natalia M.

    2013-10-01

    Microwave beam transmission and manipulation in the atmosphere is an important but difficult task. One of the major challenges in transmitting and routing microwaves in air is unavoidable divergence because of diffraction. Here we introduce and design virtual hyperbolic metamaterials (VHMMs) formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in air. Hyperbolic, or indefinite, metamaterials are photonic structures that possess permittivity and/or permeability tensor elements of opposite sign with respect to one another along principal axes, resulting in a strong anisotropy. Our proof-of-concept results confirm that the proposed virtual hyperbolic metamaterial structure can be used for efficient beam collimation and for guiding radar signals around obstacles, opening a new paradigm for electromagnetic wave manipulation in air.

  4. Large spontaneous emission rate enhancement in grating coupled hyperbolic metamaterials

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; Krishna, Koduru Hari; De Luca, Antonio; Strangi, Giuseppe

    2014-01-01

    Hyperbolic metamaterial (HMM), a sub-wavelength periodic artificial structure with hyperbolic dispersion, can enhance the spontaneous emission of quantum emitters. Here, we demonstrate the large spontaneous emission rate enhancement of an organic dye placed in a grating coupled hyperbolic metamaterial (GCHMM). A two-dimensional (2D) silver diffraction grating coupled with an Ag/Al2O3 HMM shows 18-fold spontaneous emission decay rate enhancement of dye molecules with respect to the same HMM without grating. The experimental results are compared with analytical models and numerical simulations, which confirm that the observed enhancement of GCHMM is due to the outcoupling of non-radiative plasmonic modes as well as strong plasmon-exciton coupling in HMM via diffracting grating. PMID:25209102

  5. Compaction behavior of roller compacted ibuprofen.

    PubMed

    Patel, Sarsvatkumar; Kaushal, Aditya Mohan; Bansal, Arvind Kumar

    2008-06-01

    The effect of roller compaction pressure on the bulk compaction of roller compacted ibuprofen was investigated using instrumented rotary tablet press. Three different roller pressures were utilized to prepare granules and Heckel analysis, Walker analysis, compressibility, and tabletability were performed to derive densification, deformation, course of volume reduction and bonding phenomenon of different pressure roller compacted granules. Nominal single granule fracture strength was obtained by micro tensile testing. Heckel analysis indicated that granules prepared using lower pressure during roller compaction showed lower yield strength. The reduction in tabletability was observed for higher pressure roller compacted granules. The reduction in tabletability supports the results of granule size enlargement theory. Apart from the granule size enlargement theory, the available fines and relative fragmentation during compaction is responsible for higher bonding strength and provide larger areas for true particle contact at constant porosity for lower pressure roller compacted granules. Overall bulk compaction parameters indicated that granules prepared by lower roller compaction pressure were advantageous in terms of tabletability and densification. Overall results suggested that densification during roller compaction affects the particle level properties of specific surface area, nominal fracture strength, and compaction behavior. PMID:18280716

  6. Stratified fiber bundles, Quinn homology and brane stability of hyperbolic orbifolds

    NASA Astrophysics Data System (ADS)

    Bytsenko, Andrey A.; Szabo, Richard J.; Tureanu, Anca

    2016-04-01

    We revisit the problem of stability of string vacua involving hyperbolic orbifolds using methods from homotopy theory and K-homology. We propose a definition of Type II string theory on such backgrounds that further carry stratified systems of fiber bundles, which generalize the more conventional orbifold and symmetric string backgrounds, together with a classification of wrapped branes by a suitable generalized homology theory. For spaces stratified fibered over hyperbolic orbifolds we use the algebraic K-theory of their fundamental groups and Quinn homology to derive criteria for brane stability in terms of an Atiyah-Hirzebruch type spectral sequence with its lift to K-homology. Stable D-branes in this setting carry stratified charges which induce new additive structures on the corresponding K-homology groups. We extend these considerations to backgrounds which support H-flux, where we use K-groups of twisted group algebras of the fundamental groups to analyze stability of locally symmetric spaces with K-amenable isometry groups, and derive stability conditions for branes wrapping the fibers of an Eilenberg-MacLane spectrum functor.

  7. Dynamic compaction of granular materials

    PubMed Central

    Favrie, N.; Gavrilyuk, S.

    2013-01-01

    An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding ‘intergranular stress’ coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading–unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

  8. Ceramic powder compaction

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Mahoney, F.M.

    1995-12-31

    With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

  9. Impact of hyperbolicity on chimera states in ensembles of nonlocally coupled chaotic oscillators

    NASA Astrophysics Data System (ADS)

    Semenova, N.; Zakharova, A.; Schöll, E.; Anishchenko, V.

    2016-06-01

    In this work we analyse nonlocally coupled networks of identical chaotic oscillators. We study both time-discrete and time-continuous systems (Henon map, Lozi map, Lorenz system). We hypothesize that chimera states, in which spatial domains of coherent (synchronous) and incoherent (desynchronized) dynamics coexist, can be obtained only in networks of chaotic non-hyperbolic systems and cannot be found in networks of hyperbolic systems. This hypothesis is supported by numerical simulations for hyperbolic and non-hyperbolic cases.

  10. Sharp Convergence Rate of the Glimm Scheme for General Nonlinear Hyperbolic Systems

    NASA Astrophysics Data System (ADS)

    Ancona, Fabio; Marson, Andrea

    2011-03-01

    Consider a general strictly hyperbolic, quasilinear system, in one space dimesion u_t+A(u) u_x=0,quadquadquadquadquadquad(1) where {u mapsto A(u), uinΩsubset{mathbb{R}}^N} , is a smooth matrix-valued map. Given an initial datum u(0, ·) with small total variation, let u( t, ·) be the corresponding (unique) vanishing viscosity solution of (1) obtained as a limit of solutions to the viscous parabolic approximation u t + A( u) u x = μ u xx , as μ → 0. For every T ≥ 0, we prove the a-priori bound left\\|u^{\\varepsilon}(T,\\cdot)-u(T,\\cdot)right\\|_{{mathbb{L}^1}}=o(1)\\cdotsqrt{\\varepsilon} |log{\\varepsilon}|quadquadquadquadquadquad(1) for an approximate solution {u^{\\varepsilon}} of (1) constructed by the Glimm scheme, with mesh size {Δ x = Δ t = {\\varepsilon}} , and with a suitable choice of the sampling sequence. This result provides for general hyperbolic systems the same type of error estimates valid for Glimm approximate solutions of hyperbolic systems of conservation laws u t + F( u) x = 0 satisfying the classical Lax or Liu assumptions on the eigenvalues λ k ( u) and on the eigenvectors r k ( u) of the Jacobian matrix A( u) = DF( u). The estimate (2) is obtained introducing a new wave interaction functional with a cubic term that controls the nonlinear coupling of waves of the same family and at the same time decreases at interactions by a quantity that is of the same order of the product of the wave strength times the change in the wave speeds. This is precisely the type of errors arising in a wave tracing analysis of the Glimm scheme, which is crucial to control in order to achieve an accurate estimate of the convergence rate as (2).

  11. Global solution to a hyperbolic problem arising in the modeling of blood flow in circulatory systems

    NASA Astrophysics Data System (ADS)

    Ruan, Weihua; Clark, M. E.; Zhao, Meide; Curcio, Anthony

    2007-07-01

    This paper considers a system of first-order, hyperbolic, partial differential equations in the domain of a one-dimensional network. The system models the blood flow in human circulatory systems as an initial-boundary-value problem with boundary conditions of either algebraic or differential type. The differential equations are nonhomogeneous with frictional damping terms and the state variables are coupled at internal junctions. The existence and uniqueness of the local classical solution have been established in our earlier work [W. Ruan, M.E. Clark, M. Zhao, A. Curcio, A hyperbolic system of equations of blood flow in an arterial network, J. Appl. Math. 64 (2) (2003) 637-667; W. Ruan, M.E. Clark, M. Zhao, A. Curcio, Blood flow in a network, Nonlinear Anal. Real World Appl. 5 (2004) 463-485; W. Ruan, M.E. Clark, M. Zhao, A. Curcio, A quasilinear hyperbolic system that models blood flow in a network, in: Charles V. Benton (Ed.), Focus on Mathematical Physics Research, Nova Science Publishers, Inc., New York, 2004, pp. 203-230]. This paper continues the analysis and gives sufficient conditions for the global existence of the classical solution. We prove that the solution exists globally if the boundary data satisfy the dissipative condition (2.3) or (3.2), and the norms of the initial and forcing functions in a certain Sobolev space are sufficiently small. This is only the first step toward establishing the global existence of the solution to physiologically realistic models, because, in general, the chosen dissipative conditions (2.3) and (3.2) do not appear to hold for the originally proposed boundary conditions (1.3)-(1.12).

  12. Analytic Solutions and Resonant Solutions of Hyperbolic Partial Differential Equations

    NASA Astrophysics Data System (ADS)

    Wagenmaker, Timothy Roger

    This dissertation contains two main subject areas. The first deals with solutions to the wave equation Du/Dt + a Du/Dx = 0, where D/Dt and D/Dx represent partial derivatives and a(t,x) is real valued. The question I studied, which arises in control theory, is whether solutions which are real analytic with respect to the time variable are dense in the space of all solutions. If a is real analytic in t and x, the Cauchy-Kovalevsky Theorem implies that the solutions real analytic in t and x are dense, since it suffices to approximate the initial data by polynomials. The same positive result is valid when a is continuously differentiable and independent of t. This is proved by regularization in time. The hypothesis that a is independent of t cannot be replaced by the weaker assumption that a is real analytic in t, even when it is infinitely smooth. I construct a(t,x) for which the solutions which are analytic in time are automatically periodic in time. In particular these solutions are not dense in the space of all solutions. The second area concerns the resonant interaction of oscillatory waves propagating in a compressible inviscid fluid. An asymptotic description given by Andrew Majda, Rodolfo Rosales, and Maria Schonbek (MRS) involves the genuinely nonlinear quasilinear hyperbolic system Du/Dt + D(uu/2)/Dt + v = 0, Dv/Dt - D(vv/2)/Dt - u = 0. They performed many numerical simulations which indicated that small amplitude solutions of this system tend to evade shock formation, and conjectured that "smooth initial data with a sufficiently small amplitude never develop shocks throughout a long time interval of integration.". I proved that for smooth periodic U(x), V(x) and initial data u(0,x) = epsilonU(x), v(0,x) = epsilonV(x), the solution is smooth for time at least constant times | ln epsilon| /epsilon. This is longer than the lifetime order 1/ epsilon of the solution to the decoupled Burgers equations. The decoupled equation describes nonresonant interaction of

  13. Compact Holographic Data Storage

    NASA Technical Reports Server (NTRS)

    Chao, T. H.; Reyes, G. F.; Zhou, H.

    2001-01-01

    NASA's future missions would require massive high-speed onboard data storage capability to Space Science missions. For Space Science, such as the Europa Lander mission, the onboard data storage requirements would be focused on maximizing the spacecraft's ability to survive fault conditions (i.e., no loss in stored science data when spacecraft enters the 'safe mode') and autonomously recover from them during NASA's long-life and deep space missions. This would require the development of non-volatile memory. In order to survive in the stringent environment during space exploration missions, onboard memory requirements would also include: (1) survive a high radiation environment (1 Mrad), (2) operate effectively and efficiently for a very long time (10 years), and (3) sustain at least a billion write cycles. Therefore, memory technologies requirements of NASA's Earth Science and Space Science missions are large capacity, non-volatility, high-transfer rate, high radiation resistance, high storage density, and high power efficiency. JPL, under current sponsorship from NASA Space Science and Earth Science Programs, is developing a high-density, nonvolatile and rad-hard Compact Holographic Data Storage (CHDS) system to enable large-capacity, high-speed, low power consumption, and read/write of data in a space environment. The entire read/write operation will be controlled with electrooptic mechanism without any moving parts. This CHDS will consist of laser diodes, photorefractive crystal, spatial light modulator, photodetector array, and I/O electronic interface. In operation, pages of information would be recorded and retrieved with random access and high-speed. The nonvolatile, rad-hard characteristics of the holographic memory will provide a revolutionary memory technology meeting the high radiation challenge facing the Europa Lander mission. Additional information is contained in the original extended abstract.

  14. Pointwise time asymptotic behavior of solutions to a general class of hyperbolic balance laws

    NASA Astrophysics Data System (ADS)

    Zeng, Yanni; Chen, Jiao

    2016-04-01

    In this paper we are interested in a general class of hyperbolic balance laws. Within the frame work of existence of a convex entropy function that symmetrizes the system in certain sense and the Kawashima-Shizuta condition, we study the large time behavior of the solution to the Cauchy problem in one space dimension. For a solution around a constant equilibrium state, we predetermine the asymptotic solution as a superposition of the constant state and diffusion waves along the equilibrium characteristic directions. We estimate the remainder in the pointwise sense both in space and in time. The decay rates in various directions are optimal, which further give the optimal Lp rates with 1 ≤ p ≤ ∞. Applications to several examples including the Kerr-Debye model are given.

  15. ISAR Imaging Based on the Wideband Hyperbolic Frequency-Modulation Waveform.

    PubMed

    Zhou, Wei; Yeh, Chun-mao; Jin, Kan; Yang, Jian; Lu, Yao-bin

    2015-01-01

    The hyperbolic frequency-modulated (HFM) waveform has an inherent Doppler-invariant property. It is more conducive than the conventional linear frequency-modulated (LFM) waveform to high speed moving target imaging. In order to apply the HFM waveform to existing inverse synthetic aperture radar (ISAR) imaging systems, a new pulse compression algorithm is proposed. First, the received HFM echoes are demodulated with the transmitted signal, which is called "decurve" in this paper. By this operation, the bandwidth of the demodulated echoes is effectively reduced and can be processed by the existing narrow-band receiver. Then, the phase of the decurved HFM echoes is analyzed, and thus, the pulse compression is accomplished by space-variant phase compensation. In addition, the space-variant phase compensation is realized by resampling and fast Fourier transform (FFT) with high computational efficiency. Finally, numerical results illustrate the effectiveness of the proposed method. PMID:26389901

  16. Stability analysis of numerical boundary conditions and implicit difference approximations for hyperbolic equations

    NASA Technical Reports Server (NTRS)

    Beam, R. M.; Warming, R. F.; Yee, H. C.

    1981-01-01

    Implicit, noniterative, finite difference schemes were recently developed by several authors for multidimensional systems of nonlinear hyperbolic partial differential equations. When applied to linear model equations with periodic boundary conditions those schemes are unconditionally stable (A-stable). As applied in practice the algorithms often face a severe time step restriction. A major source of the difficulty is the treatment of the numerical boundary conditions. One conjecture was that unconditional stability requires implicit numerical boundary conditions. An apparent counter example was the space time extrapolation considered by Gustafsson, Kreiss, and Sunstrom. Spatial (implicit) and space time (explicit) extrapolation using normal mode analysis for a finite and infinite number of spatial mesh intervals are examined. The results indicate that for unconditional stability with a finite number of spatial mesh intervals, the numerical boundary conditions must be implicit.

  17. ISAR Imaging Based on the Wideband Hyperbolic Frequency-Modulation Waveform

    PubMed Central

    Zhou, Wei; Yeh, Chun-mao; Jin, Kan; Yang, Jian; Lu, Yao-bin

    2015-01-01

    The hyperbolic frequency-modulated (HFM) waveform has an inherent Doppler-invariant property. It is more conducive than the conventional linear frequency-modulated (LFM) waveform to high speed moving target imaging. In order to apply the HFM waveform to existing inverse synthetic aperture radar (ISAR) imaging systems, a new pulse compression algorithm is proposed. First, the received HFM echoes are demodulated with the transmitted signal, which is called “decurve” in this paper. By this operation, the bandwidth of the demodulated echoes is effectively reduced and can be processed by the existing narrow-band receiver. Then, the phase of the decurved HFM echoes is analyzed, and thus, the pulse compression is accomplished by space-variant phase compensation. In addition, the space-variant phase compensation is realized by resampling and fast Fourier transform (FFT) with high computational efficiency. Finally, numerical results illustrate the effectiveness of the proposed method. PMID:26389901

  18. The Escape into Hyperbole: Communication and Political Correctness.

    ERIC Educational Resources Information Center

    Asante, Molefi Kete

    1992-01-01

    Maintains that political correctness as an issue is a hyperbole, and the attack on political correctness is merely the anticipated reaction to the expansion of dialogue to society's least visible populations. Discusses the First and Fourteenth Amendments to the Constitution, and argues that the twin conceptions of personal liberty and community…

  19. Infinitesimal generators and the Loewner equation on complete hyperbolic manifolds

    NASA Astrophysics Data System (ADS)

    Arosio, Leandro; Bracci, Filippo

    2011-12-01

    We characterize infinitesimal generators on complete hyperbolic complex manifolds without any regularity assumption on the Kobayashi distance. This allows to prove a general Loewner type equation with regularity of any order {d in [1, +infty]} . Finally, based on these results, we focus on some open problems naturally arising.

  20. Simple partitions of a hyperbolic plane of positive curvature

    SciTech Connect

    Romakina, Lyudmila N

    2012-09-30

    We construct special monohedral isotropic partitions with symmetries of the hyperbolic plane H of positive curvature with a simple 4-contour as a cell. An analogue of mosaic in these partitions called a tiling is introduced. Also we consider some fractal tilings. The existence of band tilings in each homological series with code (m, n) is proved. Bibliography: 14 titles.

  1. Bound states in a hyperbolic asymmetric double-well

    SciTech Connect

    Hartmann, R. R.

    2014-01-15

    We report a new class of hyperbolic asymmetric double-well whose bound state wavefunctions can be expressed in terms of confluent Heun functions. An analytic procedure is used to obtain the energy eigenvalues and the criterion for the potential to support bound states is discussed.

  2. Composite scheme using localized relaxation with non-standard finite difference method for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Kumar, Vivek; Raghurama Rao, S. V.

    2008-04-01

    Non-standard finite difference methods (NSFDM) introduced by Mickens [ Non-standard Finite Difference Models of Differential Equations, World Scientific, Singapore, 1994] are interesting alternatives to the traditional finite difference and finite volume methods. When applied to linear hyperbolic conservation laws, these methods reproduce exact solutions. In this paper, the NSFDM is first extended to hyperbolic systems of conservation laws, by a novel utilization of the decoupled equations using characteristic variables. In the second part of this paper, the NSFDM is studied for its efficacy in application to nonlinear scalar hyperbolic conservation laws. The original NSFDMs introduced by Mickens (1994) were not in conservation form, which is an important feature in capturing discontinuities at the right locations. Mickens [Construction and analysis of a non-standard finite difference scheme for the Burgers-Fisher equations, Journal of Sound and Vibration 257 (4) (2002) 791-797] recently introduced a NSFDM in conservative form. This method captures the shock waves exactly, without any numerical dissipation. In this paper, this algorithm is tested for the case of expansion waves with sonic points and is found to generate unphysical expansion shocks. As a remedy to this defect, we use the strategy of composite schemes [R. Liska, B. Wendroff, Composite schemes for conservation laws, SIAM Journal of Numerical Analysis 35 (6) (1998) 2250-2271] in which the accurate NSFDM is used as the basic scheme and localized relaxation NSFDM is used as the supporting scheme which acts like a filter. Relaxation schemes introduced by Jin and Xin [The relaxation schemes for systems of conservation laws in arbitrary space dimensions, Communications in Pure and Applied Mathematics 48 (1995) 235-276] are based on relaxation systems which replace the nonlinear hyperbolic conservation laws by a semi-linear system with a stiff relaxation term. The relaxation parameter ( λ) is chosen locally

  3. Large penetration depth of near-field heat flux in hyperbolic media

    SciTech Connect

    Lang, S. Petrov, A. Yu.; Eich, M.; Tschikin, M.; Biehs, S.-A.

    2014-03-24

    We compare super-Planckian thermal radiation between phonon-polaritonic media and hyperbolic metamaterials. In particular, we determine the penetration depth of thermal photons inside the absorbing medium for three different structures: two semi-infinite phonon-polaritonic media supporting surface modes, two multilayer hyperbolic metamaterials and two nanowire hyperbolic metamaterials. We show that for hyperbolic modes the penetration depth can be orders of magnitude larger than for surface modes suggesting that hyperbolic materials are much more preferable for near-field thermophotovoltaic applications than pure phonon-polaritonic materials.

  4. Strategy Guideline. Compact Air Distribution Systems

    SciTech Connect

    Burdick, Arlan

    2013-06-01

    This guideline discusses the benefits and challenges of using a compact air distribution system to handle the reduced loads and reduced air volume needed to condition the space within an energy efficient home. The decision criteria for a compact air distribution system must be determined early in the whole-house design process, considering both supply and return air design. However, careful installation of a compact air distribution system can result in lower material costs from smaller equipment, shorter duct runs, and fewer outlets; increased installation efficiencies, including ease of fitting the system into conditioned space; lower loads on a better balanced HVAC system, and overall improved energy efficiency of the home.

  5. Effective properties of superstructured hyperbolic metamaterials: How to beat the diffraction limit at large focal distance

    NASA Astrophysics Data System (ADS)

    Centeno, Emmanuel; Moreau, Antoine

    2015-07-01

    Superstructured hyperbolic metamaterials (HMs) have been recently introduced to realize media with effective index -1 with the ultimate goal of designing flat lenses of super-resolution power for optical imaging applications. In this work, we analyze the impact on their effective optical properties of defect metallic layers periodically added in HMs. The effective index and losses are systematically calculated in both homogenization and diffractive regimes and with respect to the ratio of dielectric and metallic layers. Although the superstructuring can dramatically decrease the effective losses, we demonstrate that the extent of the hyperbolic dispersion curve in k space plays an even more fundamental role for breaking the diffraction limit. Optimized superstructured HMs working in a regime between the homogenization and diffractive regimes are shown to present simultaneously low effective losses and a high optical resolution for visible light. These superstructured HMs present an effective index of -5 and extend the subwavelength focalization distance up to 2 λ , which is twice as large as for regular HMs.

  6. Micro-scale extensional rheometry using hyperbolic converging/diverging channels and jet breakup.

    PubMed

    Keshavarz, Bavand; McKinley, Gareth H

    2016-07-01

    Understanding the elongational rheology of dilute polymer solutions plays an important role in many biological and industrial applications ranging from microfluidic lab-on-a-chip diagnostics to phenomena such as fuel atomization and combustion. Making quantitative measurements of the extensional viscosity for dilute viscoelastic fluids is a long-standing challenge and it motivates developments in microfluidic fabrication techniques and high speed/strobe imaging of millifluidic capillary phenomena in order to develop new classes of instruments. In this paper, we study the elongational rheology of a family of dilute polymeric solutions in two devices: first, steady pressure-driven flow through a hyperbolic microfluidic contraction/expansion and, second, the capillary driven breakup of a thin filament formed from a small diameter jet ([Formula: see text]). The small length scale of the device allows very large deformation rates to be achieved. Our results show that in certain limits of low viscosity and elasticity, jet breakup studies offer significant advantages over the hyperbolic channel measurements despite the more complex implementation. Using our results, together with scaling estimates of the competing viscous, elastic, inertial and capillary timescales that control the dynamics, we construct a dimensionless map or nomogram summarizing the operating space for each instrument. PMID:27375824

  7. Compact orthogonal NMR field sensor

    DOEpatents

    Gerald, II, Rex E.; Rathke, Jerome W.

    2009-02-03

    A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

  8. FAST TRACK COMMUNICATION: Solvable nonlinear evolution PDEs in multidimensional space involving trigonometric functions

    NASA Astrophysics Data System (ADS)

    Calogero, F.; Françoise, J.-P.; Sommacal, M.

    2007-05-01

    A solvable nonlinear (system of) evolution PDEs in multidimensional space, involving trigonometric (or hyperbolic) functions, is identified. An isochronous version of this (system of) evolution PDEs in multidimensional space is also reported.

  9. Topological photonic phase in chiral hyperbolic metamaterials.

    PubMed

    Gao, Wenlong; Lawrence, Mark; Yang, Biao; Liu, Fu; Fang, Fengzhou; Béri, Benjamin; Li, Jensen; Zhang, Shuang

    2015-01-23

    Recently, the possibility of achieving one-way backscatter immune transportation of light by mimicking the topological properties of certain solid state systems, such as topological insulators, has received much attention. Thus far, however, demonstrations of nontrivial topology in photonics have relied on photonic crystals with precisely engineered lattice structures, periodic on the scale of the operational wavelength and composed of finely tuned, complex materials. Here we propose a novel effective medium approach towards achieving topologically protected photonic surface states robust against disorder on all length scales and for a wide range of material parameters. Remarkably, the nontrivial topology of our metamaterial design results from the Berry curvature arising from the transversality of electromagnetic waves in a homogeneous medium. Our investigation therefore acts to bridge the gap between the advancing field of topological band theory and classical optical phenomena such as the spin Hall effect of light. The effective medium route to topological phases will pave the way for highly compact one-way transportation of electromagnetic waves in integrated photonic circuits. PMID:25659022

  10. Compact vacuum insulation embodiments

    DOEpatents

    Benson, D.K.; Potter, T.F.

    1992-04-28

    An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially point' or line' contacts with the metal wall sheets. In the case of monolithic spacers that form line' contacts, two such spacers with the line contacts running perpendicular to each other form effectively point' contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included. 26 figs.

  11. Compact vacuum insulation

    DOEpatents

    Benson, D.K.; Potter, T.F.

    1993-01-05

    An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially point'' or line'' contacts with the metal wall sheets. In the case of monolithic spacers that form line'' contacts, two such spacers with the line contacts running perpendicular to each other form effectively point'' contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

  12. Compact vacuum insulation

    DOEpatents

    Benson, David K.; Potter, Thomas F.

    1993-01-01

    An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially "point" or "line" contacts with the metal wall sheets. In the case of monolithic spacers that form "line" contacts, two such spacers with the line contacts running perpendicular to each other form effectively "point" contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

  13. Compact vacuum insulation embodiments

    DOEpatents

    Benson, David K.; Potter, Thomas F.

    1992-01-01

    An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially "point" or "line" contacts with the metal wall sheets. In the case of monolithic spacers that form "line" contacts, two such spacers with the line contacts running perpendicular to each other form effectively "point" contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

  14. Compact SPS - Power delivery

    NASA Astrophysics Data System (ADS)

    Pospisil, M.; Pospisilova, L.

    1982-09-01

    The power deliverable by a compact solar Space Power Station (SPS) is a function of its outer surface shape. Methods of fitting the power delivery curve of such a system to different patterns of daily power demand are considered that involve the appropriate choice of the number of satellites, their maximal power, height to width ratio and the shift of longitude with respect to the receiving station. Changes in the daily delivery curve can be made by altering the longitudes and orientations of the satellites. Certain limitations to the choice of parameters exist, such as: the height to width ratio should be near 1.2, and the sum of longitude and orientation changes will probably not be greater than 50 deg. The optimization of the peak to average power ratio is also discussed.

  15. Compact vacuum insulation

    DOEpatents

    Benson, David K.; Potter, Thomas F.

    1992-01-01

    Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases therebetween are evacuated to form a vacuum. These spherical glass beads provide the maximum support while minimizing thermal conductance. In its preferred embodiment; these two metal sheets are textured with ribs or concave protrusions in conjunction with the glass beads to maximize the structural integrity of the panels while increasing the spacing between beads, thereby reducing the number of beads and the number of thermal conduction paths. Glass or porcelain-enameled liners in combination with the glass spacers and metal sidewalls effectively decrease thermal conductivity, and variious laminates, including wood, porcelain-enameled metal, and others effectively increase the strength and insulation capabilities of the panels. Also, a metal web is provided to hold the spacers in place, and strategic grooves are shown to accommodate expansion and contraction or shaping of the panels.

  16. Compact vacuum insulation

    DOEpatents

    Benson, D.K.; Potter, T.F.

    1992-10-27

    Improved compact insulation panel is provided which is comprised of two adjacent metal sheets spaced close together with a plurality of spherical, or other discretely shaped, glass or ceramic beads optimally positioned between the sheets to provide support and maintain the spacing between the metal sheets when the gases there between are evacuated to form a vacuum. These spherical glass beads provide the maximum support while minimizing thermal conductance. In its preferred embodiment; these two metal sheets are textured with ribs or concave protrusions in conjunction with the glass beads to maximize the structural integrity of the panels while increasing the spacing between beads, thereby reducing the number of beads and the number of thermal conduction paths. Glass or porcelain-enameled liners in combination with the glass spacers and metal sidewalls effectively decrease thermal conductivity, and various laminates, including wood, porcelain-enameled metal, and others effectively increase the strength and insulation capabilities of the panels. Also, a metal web is provided to hold the spacers in place, and strategic grooves are shown to accommodate expansion and contraction or shaping of the panels. 35 figs.

  17. A Compact Trench-Assisted Multi-Orbital-Angular-Momentum Multi-Ring Fiber for Ultrahigh-Density Space-Division Multiplexing (19 Rings × 22 Modes)

    PubMed Central

    Li, Shuhui; Wang, Jian

    2014-01-01

    We present a compact (130 μm cladding diameter) trench-assisted multi-orbital-angular-momentum (OAM) multi-ring fiber with 19 rings each supporting 22 modes with 18 OAM ones. Using the high-contrast-index ring and trench designs, the trench-assisted multi-OAM multi-ring fiber (TA-MOMRF) features both low-level inter-mode crosstalk and inter-ring crosstalk within a wide wavelength range (1520 to 1630 nm), which can potentially enable Pbit/s total transmission capacity and hundreds bit/s/Hz spectral efficiency in a single TA-MOMRF. Moreover, the effective refractive index difference of even and odd fiber eigenmodes induced by the ellipticity of ring and fiber bending and their impacts on the purity of OAM mode and mode coupling/crosstalk are analyzed. It is found that high-order OAM modes show preferable tolerance to the ring ellipticity and fiber bending. The designed fiber offers favorable tolerance to both small ellipticity of ring (<−22 dB crosstalk under an ellipticity of 0.5%) and small bend radius (<−20 dB crosstalk under a bend radius of 2 cm). PMID:24458159

  18. Hamiltonians for the Quantum Hall Effect on Spaces with Non-Constant Metrics

    NASA Astrophysics Data System (ADS)

    Bracken, Paul Francis

    2007-01-01

    The problem of studying the quantum Hall effect on manifolds with non constant metric is addressed. The Hamiltonian on a space with hyperbolic metric is determined, and the spectrum and eigenfunctions are calculated in closed form. The hyperbolic disk is also considered and some other applications of this approach are discussed as well.

  19. Compact Color Schlieren Optical System

    NASA Technical Reports Server (NTRS)

    Buchele, Donald R.; Griffin, Devon W.

    1996-01-01

    Compact, rugged optical system developed for use in rainbow schlieren deflectometry. Features unobscured telescope with focal-length/aperture-width ratio of 30. Made of carefully selected but relatively inexpensive parts. All of lenses stock items. By-product of design is optical system with loose tolerances on interlens spacing. One of resulting advantages, insensitivity to errors in fabrication of optomechanical mounts. Another advantage is ability to compensate for some of unit-to-unit variations inherent in stock lenses.

  20. Superkicks in hyperbolic encounters of binary black holes.

    PubMed

    Healy, James; Herrmann, Frank; Hinder, Ian; Shoemaker, Deirdre M; Laguna, Pablo; Matzner, Richard A

    2009-01-30

    Generic inspirals and mergers of binary black holes produce beamed emission of gravitational radiation that can lead to a gravitational recoil or kick of the final black hole. The kick velocity depends on the mass ratio and spins of the binary as well as on the dynamics of the binary configuration. Studies have focused so far on the most astrophysically relevant configuration of quasicircular inspirals, for which kicks as large as approximately 3300 km s;(-1) have been found. We present the first study of gravitational recoil in hyperbolic encounters. Contrary to quasicircular configurations, in which the beamed radiation tends to average during the inspiral, radiation from hyperbolic encounters is plunge dominated, resulting in an enhancement of preferential beaming. As a consequence, it is possible in highly relativistic scatterings to achieve kick velocities as large as 10 000 km s;(-1). PMID:19257409

  1. Hyperbolicity of physical theories with application to general relativity

    NASA Astrophysics Data System (ADS)

    Hilditch, David; Richter, Ronny

    2016-08-01

    We consider gauge theories from the free evolution point of view, in which initial data satisfying constraints of a theory are given, and because the constraints satisfy a closed evolution system, they remain so. We study a model constrained Hamiltonian theory and identify a particular structure in the equations of motion which we call the standard gauge freedom. The pure gauge subsystem of this model theory is identified, and the manner in which the gauge variables couple to the field equations is presented. We demonstrate that the set of gauge choices that can be coupled to the field equations to obtain a strongly hyperbolic formulation is exactly the set of strongly hyperbolic pure gauges. Consequently we analyze a parametrized family of formulations of general relativity. The generalization of the harmonic gauge formulation to a five parameter family of gauge conditions is obtained.

  2. Topological insulators are tunable waveguides for hyperbolic polaritons

    NASA Astrophysics Data System (ADS)

    Wu, Jhih-Sheng; Basov, Dimitri; Fogler, Michael

    We present a theoretical analysis showing that layered topological insulators, for example, Bi2Se3 are optically hyperbolic materials in a range of THz frequencies. As such, these topological insulators possess deeply subdiffractional, highly directional collective modes: hyperbolic phonon-polaritons. We predict that in thin crystals the dispersion of these modes is split into discrete subbands and is strongly influenced by electron surface states. If the surface states are doped, then hybrid collective modes result from coupling of the phonon-polaritons with surface plasmons. The strength of the hybridization can be controlled by an external gate that varies the chemical potential of the surface states. We also show that momentum-dependence of the plasmon-phonon coupling leads to a polaritonic analog of the Goos-Hänchen effect. Directionality of the polaritonic rays and their tunable Goos-Hänchen shift are observable via THz nanoimaging.

  3. Topological insulators are tunable waveguides for hyperbolic polaritons

    NASA Astrophysics Data System (ADS)

    Wu, Jhih-Sheng; Basov, D. N.; Fogler, M. M.

    2015-11-01

    We present a theoretical analysis showing that layered topological insulators, for example, Bi2Se3 are optically hyperbolic materials in the range of terahertz (THz) frequencies. As such, these topological insulators possess deeply subdiffractional, highly directional collective modes: hyperbolic phonon polaritons. We predict that in thin crystals the dispersion of these modes is split into discrete subbands and is strongly influenced by electron surface states. If the surface states are doped, then hybrid collective modes result from coupling of the phonon polaritons with surface plasmons. The strength of the hybridization can be controlled by an external gate that varies the chemical potential of the surface states. We also show that the momentum dependence of the plasmon-phonon coupling leads to a polaritonic analog of the Goos-Hänchen effect. The directionality of the polaritonic rays and their tunable Goos-Hänchen shift is observable via THz nanoimaging.

  4. Propagation of electromagnetic waves in P T -symmetric hyperbolic structures

    NASA Astrophysics Data System (ADS)

    Shramkova, O. V.; Tsironis, G. P.

    2016-07-01

    We investigate theoretically and numerically the propagation of electromagnetic waves in P T -symmetric periodic stacks composed of hyperbolic metamaterial layers separated by dielectric media with balanced loss and gain. We derive the characteristic frequencies governing the dispersion properties of the eigenwaves of P T -symmetric semiconductor-dielectric stacks. By tuning the loss/gain level and thicknesses of the layers, we study the evolution of the dispersion dependencies. We show that the effective-medium approach does not adequately describe the propagating waves in the P T -symmetric hypercrystals, even for wavelengths that are about 100 times larger than the period of the stack. We demonstrate the existence of anisotropic transmission resonances and above-unity reflection in P T -symmetric hyperbolic systems. The P T -symmetry-breaking transition of the scattering matrix is strongly influenced by the constitutive and geometrical parameters of the layers and the angles of wave incidence.

  5. Operator-Based Preconditioning of Stiff Hyperbolic Systems

    SciTech Connect

    Reynolds, Daniel R.; Samtaney, Ravi; Woodward, Carol S.

    2009-02-09

    We introduce an operator-based scheme for preconditioning stiff components encoun- tered in implicit methods for hyperbolic systems of partial differential equations posed on regular grids. The method is based on a directional splitting of the implicit operator, followed by a char- acteristic decomposition of the resulting directional parts. This approach allows for solution to any number of characteristic components, from the entire system to only the fastest, stiffness-inducing waves. We apply the preconditioning method to stiff hyperbolic systems arising in magnetohydro- dynamics and gas dynamics. We then present numerical results showing that this preconditioning scheme works well on problems where the underlying stiffness results from the interaction of fast transient waves with slowly-evolving dynamics, scales well to large problem sizes and numbers of processors, and allows for additional customization based on the specific problems under study.

  6. On Another Edge of Defocusing: Hyperbolicity of Asymmetric Lemon Billiards

    NASA Astrophysics Data System (ADS)

    Bunimovich, Leonid; Zhang, Hong-Kun; Zhang, Pengfei

    2016-02-01

    Defocusing mechanism provides a way to construct chaotic (hyperbolic) billiards with focusing components by separating all regular components of the boundary of a billiard table sufficiently far away from each focusing component. If all focusing components of the boundary of the billiard table are circular arcs, then the above separation requirement reduces to that all circles obtained by completion of focusing components are contained in the billiard table. In the present paper we demonstrate that a class of convex tables— asymmetric lemons, whose boundary consists of two circular arcs, generate hyperbolic billiards. This result is quite surprising because the focusing components of the asymmetric lemon table are extremely close to each other, and because these tables are perturbations of the first convex ergodic billiard constructed more than 40 years ago.

  7. A novel hyperbolic grid generation procedure with inherent adaptive dissipation

    SciTech Connect

    Tai, C.H.; Yin, S.L.; Soong, C.Y.

    1995-01-01

    This paper reports a novel hyperbolic grid-generation with an inherent adaptive dissipation (HGAD), which is capable of improving the oscillation and overlapping of grid lines. In the present work upwinding differencing is applied to discretize the hyperbolic system and, thereby, to develop the adaptive dissipation coefficient. Complex configurations with the features of geometric discontinuity, exceptional concavity and convexity are used as the test cases for comparison of the present HGAD procedure with the conventional hyerbolic and elliptic ones. The results reveal that the HGAD method is superior in orthogonality and smoothness of the grid system. In addition, the computational efficiency of the flow solver may be improved by using the present HGAD procedure. 15 refs., 8 figs.

  8. Subwavelength focusing of terahertz waves in silicon hyperbolic metamaterials.

    PubMed

    Kannegulla, Akash; Cheng, Li-Jing

    2016-08-01

    We theoretically demonstrate the subwavelength focusing of terahertz (THz) waves in a hyperbolic metamaterial (HMM) based on a two-dimensional subwavelength silicon pillar array microstructure. The silicon microstructure with a doping concentration of at least 1017  cm-3 offers a hyperbolic dispersion at terahertz frequency range and promises the focusing of terahertz Gaussian beams. The results agree with the simulation based on effective medium theory. The focusing effect can be controlled by the doping concentration, which determines the real part of the out-of-plane permittivity and, therefore, the refraction angles in HMM. The focusing property in the HMM structure allows the propagation of terahertz wave through a subwavelength aperture. The silicon-based HMM structure can be realized using microfabrication technologies and has the potential to advance terahertz imaging with subwavelength resolution. PMID:27472613

  9. Generalized Lamé functions. II. Hyperbolic and trigonometric specializations

    NASA Astrophysics Data System (ADS)

    Ruijsenaars, S. N. M.

    1999-03-01

    In Part I [J. Math. Phys. 40, 1595 (1999)] we studied eigenfunctions of the quantum dynamics that defines the two-particle relativistic Calogero-Moser system with elliptic interaction. In the present paper we consider the same system with hyperbolic and trigonometric interactions. In these special regimes the eigenfunctions are shown to admit an elementary representation that is far more explicit than the "zero representation" of Part I. In particular, the new representation can be exploited to prove that the hyperbolic eigenfunctions can be chosen to be symmetric under interchanging position and momentum variables (self-duality). In the trigonometric case duality properties are derived, too, and several orthogonality and completeness results are obtained.

  10. Near-field energy extraction with hyperbolic metamaterials.

    PubMed

    Shi, Jiawei; Liu, Baoan; Li, Pengfei; Ng, Li Yen; Shen, Sheng

    2015-02-11

    Although blackbody radiation described by Planck's law is commonly regarded as the maximum of thermal radiation, thermal energy transfer in the near-field can exceed the blackbody limit due to the contribution from evanescent waves. Here, we demonstrate experimentally a broadband thermal energy extraction device based on hyperbolic metamaterials that can significantly enhance near-field thermal energy transfer. The thermal extractor made from hyperbolic metamaterials does not absorb or emit any radiation but serves as a transparent pipe guiding the radiative energy from the emitter. At the same gap between an emitter and an absorber, we observe that near-field thermal energy transfer with thermal extraction can be enhanced by around 1 order of magnitude, compared to the case without thermal extraction. The novel thermal extraction scheme has important practical implications in a variety of technologies, e.g., thermophotovoltaic energy conversion, radiative cooling, thermal infrared imaging, and heat assisted magnetic recording. PMID:25622221

  11. Generating partitions for two-dimensional hyperbolic maps

    NASA Astrophysics Data System (ADS)

    Bäcker, A.; Chernov, N.

    1998-01-01

    For a class of two-dimensional hyperbolic maps (which includes certain billiard systems) we construct finite generating partitions. Thus, trajectories of the map can be labelled uniquely by doubly infinite symbol sequences, where the symbols correspond to the atoms of the partition. It is shown that the corresponding conditions are fulfilled in the case of the cardioid billiard, the stadium billiard (and other Bunimovich billiards), planar dispersing and semidispersing billiards.

  12. Solving MPCC Problem with the Hyperbolic Penalty Function

    NASA Astrophysics Data System (ADS)

    Melo, Teófilo; Monteiro, M. Teresa T.; Matias, João

    2011-09-01

    The main goal of this work is to solve mathematical program with complementarity constraints (MPCC) using nonlinear programming techniques (NLP). An hyperbolic penalty function is used to solve MPCC problems by including the complementarity constraints in the penalty term. This penalty function [1] is twice continuously differentiable and combines features of both exterior and interior penalty methods. A set of AMPL problems from MacMPEC [2] are tested and a comparative study is performed.

  13. Asymptotic stability of relaxation shock profiles for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Liu, Hailiang

    This paper studies the asymptotic stability of traveling relaxation shock profiles for hyperbolic systems of conservation laws. Under a stability condition of subcharacteristic type the large time relaxation dynamics on the level of shocks is shown to be determined by the equilibrium conservation laws. The proof is due to the energy principle, using the weighted norms, the interaction of waves from various modes is treated by imposing suitable weight matrix.

  14. High-resolution schemes for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Harten, A.

    1982-01-01

    A class of new explicit second order accurate finite difference schemes for the computation of weak solutions of hyperbolic conservation laws is presented. These highly nonlinear schemes are obtained by applying a nonoscillatory first order accurae scheme to an appropriately modified flux function. The so derived second order accurate schemes achieve high resolution while preserving the robustness of the original nonoscillatory first order accurate scheme.

  15. An iterative method for systems of nonlinear hyperbolic equations

    NASA Technical Reports Server (NTRS)

    Scroggs, Jeffrey S.

    1989-01-01

    An iterative algorithm for the efficient solution of systems of nonlinear hyperbolic equations is presented. Parallelism is evident at several levels. In the formation of the iteration, the equations are decoupled, thereby providing large grain parallelism. Parallelism may also be exploited within the solves for each equation. Convergence of the interation is established via a bounding function argument. Experimental results in two-dimensions are presented.

  16. Uniform global existence and parabolic limit for partially dissipative hyperbolic systems

    NASA Astrophysics Data System (ADS)

    Peng, Yue-Jun; Wasiolek, Victor

    2016-05-01

    This work concerns smooth solutions to the Cauchy problem for first-order partially dissipative hyperbolic systems with a small parameter. The systems are written in non-conservative form in several space variables. We introduce algebraic conditions on the structure of the systems. Under these conditions together with a partial dissipation condition and the Shizuta-Kawashima stability condition, we prove three main results around constant equilibrium states. These results are uniform global existence with respect to the parameter, global-in-time convergence of the systems to second-order nonlinear parabolic systems in a slow time variable, and global existence when the parameter is fixed. We also give examples of physical models to which the above results can be applied.

  17. From explosive to infinite-order transitions on a hyperbolic network

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Brunson, C. T.; Boettcher, Stefan

    2014-11-01

    We analyze the phase transitions that emerge from the recursive design of certain hyperbolic networks that includes, for instance, a discontinuous ("explosive") transition in ordinary percolation. To this end, we solve the q -state Potts model in the analytic continuation for noninteger q with the real-space renormalization group. We find exact expressions for this one-parameter family of models that describe the dramatic transformation of the transition. In particular, this variation in q shows that the discontinuous transition is generic in the regime q <2 that includes percolation. A continuous ferromagnetic transition is recovered in a singular manner only for the Ising model, q =2 . For q >2 the transition immediately transforms into an infinitely smooth order parameter of the Berezinskii-Kosterlitz-Thouless type.

  18. Emission and propagation of hyperbolic phonon polaritons in hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Dai, Siyuan; Ma, Qiong; Yang, Yafang; Rosenfeld, Jeremy; Goldflam, Michael; McLeod, Alex; Andersen, Trond; Fei, Zhe; Liu, Mengkun; Sun, Zhiyuan; Shao, Yinming; Watanabe, Kenji; Taniguchi, Takashi; Thiemens, Mark; Keilmann, Fritz; Jarillo-Herrero, Pablo; Fogler, Michael; Basov, D. N.

    Using scattering-type scanning near-field optical microscope (s-SNOM), we studied various kinds of emission and propagation of hyperbolic phonon polaritons (HP2s) in hexagonal boron nitride (hBN). The systematic study via real-space nano-imaging reveals the emission mechanisms and propagating properties of HP2s excited by crystal edges, artificial structures, surface defects and impurities. Compared with traditional s-SNOM tip emitter, the polaritons from new emitters reported in this work possess longer propagation length and can be artificially manipulated on the hBN surface. Our work may benefit the future applications and engineering of HP2s using convenient emitters which are analogous to collective modes in other materials.

  19. A Second-Order Iterative Implicit Explicit Hybrid Scheme for Hyperbolic Systems of Conservation Laws

    NASA Astrophysics Data System (ADS)

    Dai, Wenlong; Woodward, Paul R.

    1996-10-01

    An iterative implicit-explicit hybrid scheme is proposed for hyperbolic systems of conservation laws. Each wave in a system may be implicitly, or explicitly, or partially implicitly and partially explicitly treated depending on its associated Courant number in each numerical cell, and the scheme is able to smoothly switch between implicit and explicit calculations. The scheme is of Godunov-type in both explicit and implicit regimes, is in a strict conservation form, and is accurate to second-order in both space and time for all Courant numbers. The computer code for the scheme is easy to vectorize. Multicolors proposed in this paper may reduce the number of iterations required to reach a converged solution by several orders for a large time step. The feature of the scheme is shown through numerical examples.

  20. Mid-infrared hyperbolic metamaterial based on graphene-dielectric multilayers

    NASA Astrophysics Data System (ADS)

    Chang, You-Chia; Kildishev, Alexander V.; Narimanov, Evgenii E.; Liu, Che-Hung; Liu, Chang-Hua; Zhang, Siyuan; Marder, Seth R.; Zhong, Zhaohui; Norris, Theodore B.

    2015-09-01

    Graphene-based hyperbolic metamaterials (HMMs) enable new possibilities that are not attainable with conventional metal-based HMMs, such as tunability of optical properties and the ability to combine with graphene-based photodetection. A graphene HMM is made of alternating graphene-dielectric multilayers, whose properties can be understood with the effective-medium approximation (EMA). The initial experimental realization of this novel metamaterial has been demonstrated with a far-field measurement, and in this paper we investigate the light coupling from free space into a graphene HMM slab with a metallic grating using numerical simulations. We show that light can be efficiently coupled into the high-k guided modes in the HMM slab and be absorbed by the graphene layers, which can be applied to create ultrathin super absorbers.

  1. Well-balanced high-order centred schemes for non-conservative hyperbolic systems. Applications to shallow water equations with fixed and mobile bed

    NASA Astrophysics Data System (ADS)

    Canestrelli, Alberto; Siviglia, Annunziato; Dumbser, Michael; Toro, Eleuterio F.

    2009-06-01

    This paper concerns the development of high-order accurate centred schemes for the numerical solution of one-dimensional hyperbolic systems containing non-conservative products and source terms. Combining the PRICE-T method developed in [Toro E, Siviglia A. PRICE: primitive centred schemes for hyperbolic system of equations. Int J Numer Methods Fluids 2003;42:1263-91] with the theoretical insights gained by the recently developed path-conservative schemes [Castro M, Gallardo J, Parés C. High-order finite volume schemes based on reconstruction of states for solving hyperbolic systems with nonconservative products applications to shallow-water systems. Math Comput 2006;75:1103-34; Parés C. Numerical methods for nonconservative hyperbolic systems: a theoretical framework. SIAM J Numer Anal 2006;44:300-21], we propose the new PRICE-C scheme that automatically reduces to a modified conservative FORCE scheme if the underlying PDE system is a conservation law. The resulting first-order accurate centred method is then extended to high order of accuracy in space and time via the ADER approach together with a WENO reconstruction technique. The well-balanced properties of the PRICE-C method are investigated for the shallow water equations. Finally, we apply the new scheme to the shallow water equations with fix bottom topography and with variable bottom solving an additional sediment transport equation.

  2. A local pseudo arc-length method for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Wang, Xing; Ma, Tian-Bao; Ren, Hui-Lan; Ning, Jian-Guo

    2014-12-01

    A local pseudo arc-length method (LPALM) for solving hyperbolic conservation laws is presented in this paper. The key idea of this method comes from the original arc-length method, through which the critical points are bypassed by transforming the computational space. The method is based on local changes of physical variables to choose the discontinuous stencil and introduce the pseudo arc-length parameter, and then transform the governing equations from physical space to arc-length space. In order to solve these equations in arc-length coordinate, it is necessary to combine the velocity of mesh points in the moving mesh method, and then convert the physical variable in arclength space back to physical space. Numerical examples have proved the effectiveness and generality of the new approach for linear equation, nonlinear equation and system of equations with discontinuous initial values. Non-oscillation solution can be obtained by adjusting the parameter and the mesh refinement number for problems containing both shock and rarefaction waves.

  3. New avenues for phase matching in nonlinear hyperbolic metamaterials.

    PubMed

    Duncan, C; Perret, L; Palomba, S; Lapine, M; Kuhlmey, B T; de Sterke, C Martijn

    2015-01-01

    Nonlinear optical processes, which are of paramount importance in science and technology, involve the generation of new frequencies. This requires phase matching to avoid that light generated at different positions interferes destructively. Of the two original approaches to achieve this, one relies on birefringence in optical crystals, and is therefore limited by the dispersion of naturally occurring materials, whereas the other, quasi-phase-matching, requires direct modulation of material properties, which is not universally possible. To overcome these limitations, we propose to exploit the unique dispersion afforded by hyperbolic metamaterials, where the refractive index can be arbitrarily large. We systematically analyse the ensuing opportunities and demonstrate that hyperbolic phase matching can be achieved with a wide range of material parameters, offering access to the use of nonlinear media for which phase matching cannot be achieved by other means. With the rapid development in the fabrication of hyperbolic metamaterials, our approach is destined to bring significant advantages over conventional techniques for the phase matching of a variety of nonlinear processes. PMID:25757863

  4. Inverse scattering at fixed energy on asymptotically hyperbolic Liouville surfaces

    NASA Astrophysics Data System (ADS)

    Daudé, Thierry; Kamran, Niky; Nicoleau, Francois

    2015-12-01

    In this paper, we study an inverse scattering problem on Liouville surfaces having two asymptotically hyperbolic ends. The main property of Liouville surfaces consists of the complete separability of the Hamilton-Jacobi equations for the geodesic flow. An important related consequence is the fact that the stationary wave equation can be separated into a system of radial and angular ODEs. The full scattering matrix at fixed energy associated to a scalar wave equation on asymptotically hyperbolic Liouville surfaces can be thus simplified by considering its restrictions onto the generalized harmonics corresponding to the angular separated ODE. The resulting partial scattering matrices consists in a countable set of 2 × 2 matrices whose coefficients are the so called transmission and reflection coefficients. It is shown that the reflection coefficients are nothing but generalized Weyl-Titchmarsh (WT) functions for the radial ODE in which the generalized angular momentum is seen as the spectral parameter. Using the complex angular momentum method and recent results on 1D inverse problem from generalized WT functions, we show that the knowledge of the reflection operators at a fixed non-zero energy is enough to determine uniquely the metric of the asymptotically hyperbolic Liouville surface under consideration.

  5. Hyperbolic method for magnetic reconnection process in steady state magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Baty, Hubert; Nishikawa, Hiroaki

    2016-06-01

    A recent numerical approach for solving the advection-diffusion and Navier-Stokes equations is extended for the first time to a magnetohydrodynamic (MHD) model, aiming in particular consistent improvements over classical methods for investigating the magnetic reconnection process. In this study, we mainly focus on a two-dimensional incompressible set of resistive MHD equations written in flux-vorticity scalar variables. The originality of the method is based on hyperbolic reformulation of the dissipative terms, leading to the construction of an equivalent hyperbolic first-order (spatial derivatives) system. This enables the use of approximate Riemann solvers for handling dissipative and advective flux in the same way. A simple second-order finite-volume discretization on rectangular grids using an upwind flux is employed. The advantages of this method are illustrated by a comparison to two particular analytical steady state solutions of the inviscid magnetic reconnection mechanism, namely the magnetic annihilation and the reconnective diffusion problems. In particular, the numerical solution is obtained with the same order of accuracy for the solution and gradient for a wide range of magnetic Reynolds numbers, without any deterioration characteristic of more conventional schemes. The amelioration of the hyperbolic method and its extension to time-dependent MHD problems related to solar flares mechanisms is also discussed.

  6. Space.

    ERIC Educational Resources Information Center

    Web Feet K-8, 2001

    2001-01-01

    This annotated subject guide to Web sites and additional resources focuses on space and astronomy. Specifies age levels for resources that include Web sites, CD-ROMS and software, videos, books, audios, and magazines; offers professional resources; and presents a relevant class activity. (LRW)

  7. Compact neutron generator

    DOEpatents

    Leung, Ka-Ngo; Lou, Tak Pui

    2005-03-22

    A compact neutron generator has at its outer circumference a toroidal shaped plasma chamber in which a tritium (or other) plasma is generated. A RF antenna is wrapped around the plasma chamber. A plurality of tritium ion beamlets are extracted through spaced extraction apertures of a plasma electrode on the inner surface of the toroidal plasma chamber and directed inwardly toward the center of neutron generator. The beamlets pass through spaced acceleration and focusing electrodes to a neutron generating target at the center of neutron generator. The target is typically made of titanium tubing. Water is flowed through the tubing for cooling. The beam can be pulsed rapidly to achieve ultrashort neutron bursts. The target may be moved rapidly up and down so that the average power deposited on the surface of the target may be kept at a reasonable level. The neutron generator can produce fast neutrons from a T-T reaction which can be used for luggage and cargo interrogation applications. A luggage or cargo inspection system has a pulsed T-T neutron generator or source at the center, surrounded by associated gamma detectors and other components for identifying explosives or other contraband.

  8. Mouse Embryo Compaction.

    PubMed

    White, M D; Bissiere, S; Alvarez, Y D; Plachta, N

    2016-01-01

    Compaction is a critical first morphological event in the preimplantation development of the mammalian embryo. Characterized by the transformation of the embryo from a loose cluster of spherical cells into a tightly packed mass, compaction is a key step in the establishment of the first tissue-like structures of the embryo. Although early investigation of the mechanisms driving compaction implicated changes in cell-cell adhesion, recent work has identified essential roles for cortical tension and a compaction-specific class of filopodia. During the transition from 8 to 16 cells, as the embryo is compacting, it must also make fundamental decisions regarding cell position, polarity, and fate. Understanding how these and other processes are integrated with compaction requires further investigation. Emerging imaging-based techniques that enable quantitative analysis from the level of cell-cell interactions down to the level of individual regulatory molecules will provide a greater understanding of how compaction shapes the early mammalian embryo. PMID:27475854

  9. PICOBIT: A Compact Scheme System for Microcontrollers

    NASA Astrophysics Data System (ADS)

    St-Amour, Vincent; Feeley, Marc

    Due to their tight memory constraints, small microcontroller based embedded systems have traditionally been implemented using low-level languages. This paper shows that the Scheme programming language can also be used for such applications, with less than 7 kB of total memory. We present PICOBIT, a very compact implementation of Scheme suitable for memory constrained embedded systems. To achieve a compact system we have tackled the space issue in three ways: the design of a Scheme compiler generating compact bytecode, a small virtual machine, and an optimizing C compiler suited to the compilation of the virtual machine.

  10. Compact, Reliable EEPROM Controller

    NASA Technical Reports Server (NTRS)

    Katz, Richard; Kleyner, Igor

    2010-01-01

    A compact, reliable controller for an electrically erasable, programmable read-only memory (EEPROM) has been developed specifically for a space-flight application. The design may be adaptable to other applications in which there are requirements for reliability in general and, in particular, for prevention of inadvertent writing of data in EEPROM cells. Inadvertent writes pose risks of loss of reliability in the original space-flight application and could pose such risks in other applications. Prior EEPROM controllers are large and complex and do not provide all reasonable protections (in many cases, few or no protections) against inadvertent writes. In contrast, the present controller provides several layers of protection against inadvertent writes. The controller also incorporates a write-time monitor, enabling determination of trends in the performance of an EEPROM through all phases of testing. The controller has been designed as an integral subsystem of a system that includes not only the controller and the controlled EEPROM aboard a spacecraft but also computers in a ground control station, relatively simple onboard support circuitry, and an onboard communication subsystem that utilizes the MIL-STD-1553B protocol. (MIL-STD-1553B is a military standard that encompasses a method of communication and electrical-interface requirements for digital electronic subsystems connected to a data bus. MIL-STD- 1553B is commonly used in defense and space applications.) The intent was to both maximize reliability while minimizing the size and complexity of onboard circuitry. In operation, control of the EEPROM is effected via the ground computers, the MIL-STD-1553B communication subsystem, and the onboard support circuitry, all of which, in combination, provide the multiple layers of protection against inadvertent writes. There is no controller software, unlike in many prior EEPROM controllers; software can be a major contributor to unreliability, particularly in fault

  11. Hyperbolic Orbits and the Planetary Flylby Anomaly

    NASA Technical Reports Server (NTRS)

    Wilson, T.L.; Blome, H.J.

    2009-01-01

    Space probes in the Solar System have experienced unexpected changes in velocity known as the flyby anomaly [1], as well as shifts in acceleration referred to as the Pioneer anomaly [2-4]. In the case of Earth flybys, ESA s Rosetta spacecraft experienced the flyby effect and NASA s Galileo and NEAR satellites did the same, although MESSENGER did not possibly due to a latitudinal property of gravity assists. Measurements indicate that both anomalies exist, and explanations have varied from the unconventional to suggestions that new physics in the form of dark matter might be the cause of both [5]. Although dark matter has been studied for over 30 years, there is as yet no strong experimental evidence supporting it [6]. The existence of dark matter will certainly have a significant impact upon ideas regarding the origin of the Solar System. Hence, the subject is very relevant to planetary science. We will point out here that one of the fundamental problems in science, including planetary physics, is consistency. Using the well-known virial theorem in astrophysics, it will be shown that present-day concepts of orbital mechanics and cosmology are not consistent for reasons having to do with the flyby anomaly. Therefore, the basic solution regarding the anomalies should begin with addressing the inconsistencies first before introducing new physics.

  12. Reversible DNA compaction.

    PubMed

    González-Pérez, Alfredo

    2014-01-01

    In this review we summarize and discuss the different methods we can use to achieve reversible DNA compaction in vitro. Reversible DNA compaction is a natural process that occurs in living cells and viruses. As a result these process long sequences of DNA can be concentrated in a small volume (compacted) to be decompacted only when the information carried by the DNA is needed. In the current work we review the main artificial compacting agents looking at their suitability for decompaction. The different approaches used for decompaction are strongly influenced by the nature of the compacting agent that determines the mechanism of compaction. We focus our discussion on two main artificial compacting agents: multivalent cations and cationic surfactants that are the best known compacting agents. The reversibility of the process can be achieved by adding chemicals like divalent cations, alcohols, anionic surfactants, cyclodextrins or by changing the chemical nature of the compacting agents via pH modifications, light induced conformation changes or by redox-reactions. We stress the relevance of electrostatic interactions and self-assembly as a main approach in order to tune up the DNA conformation in order to create an on-off switch allowing a transition between coil and compact states. The recent advances to control DNA conformation in vitro, by means of molecular self-assembly, result in a better understanding of the fundamental aspects involved in the DNA behavior in vivo and serve of invaluable inspiration for the development of potential biomedical applications. PMID:24444152

  13. Compaction processes in granular beds composed of different particle sizes

    NASA Astrophysics Data System (ADS)

    Lowe, C. A.; Greenaway, M. W.

    2005-12-01

    A piston impacting a granular bed will cause the material to compact; the strength of a granular bed is significant during weak impact relating to piston speeds of 100m/s. The strength associated with the granular structure is described as the intergranular stress; this is the resistance of a granular bed to compaction which can be measured by carefully constructing experiments. The compaction process may then be modeled by solving a hyperbolic system of equations that utilizes these data to close the system. The compaction behavior of a porous material is particle-size dependent; to accurately describe the response of two granular beds that may be of different particle sizes and distributions, it is essential that the intergranular stress is derived for each particle bed. This work uses recent compaction experiments to derive intergranular stress curves for prepressed conventional HMX material that is of nonuniform distribution with a mean diameter of 40μm and a microfine HMX of more uniform distribution of mean diameter <5μm. Steady-state compaction waves in the solid material are analyzed: initially the solid is assumed to behave as an incompressible medium. The speed and extent of compaction can be simply determined through the solution of a quadratic equation. Following this, the assumption is relaxed allowing changes in solid-phase density; a complicated equation of state makes the use of numerical methods mandatory. The speed of steady-state waves in HMX due to low impact compaction can be determined within 2% accuracy using the simple closed solution based on solid incompressibility, which is a function of the initial material porosity and density, piston speed, and the intergranular stress of the granular bed. This analysis reveals the difference between the weak impact response of a coarse nonuniform bed and a fine almost uniform granular bed that are initially loaded to 75% of the theoretical maximum density. The fine particle beds have increased

  14. Rapid compaction during RNA folding

    NASA Astrophysics Data System (ADS)

    Russell, Rick; Millett, Ian S.; Tate, Mark W.; Kwok, Lisa W.; Nakatani, Bradley; Gruner, Sol M.; Mochrie, Simon G. J.; Pande, Vijay; Doniach, Sebastian; Herschlag, Daniel; Pollack, Lois

    2002-04-01

    We have used small angle x-ray scattering and computer simulations with a coarse-grained model to provide a time-resolved picture of the global folding process of the Tetrahymena group I RNA over a time window of more than five orders of magnitude. A substantial phase of compaction is observed on the low millisecond timescale, and the overall compaction and global shape changes are largely complete within one second, earlier than any known tertiary contacts are formed. This finding indicates that the RNA forms a nonspecifically collapsed intermediate and then searches for its tertiary contacts within a highly restricted subset of conformational space. The collapsed intermediate early in folding of this RNA is grossly akin to molten globule intermediates in protein folding.

  15. Dynamics in non-globally-hyperbolic static spacetimes: II. General analysis of prescriptions for dynamics

    NASA Astrophysics Data System (ADS)

    Ishibashi, Akihiro; Wald, Robert M.

    2003-08-01

    It was previously shown by one of us that in any static, non-globally-hyperbolic, spacetime, it is always possible to define a sensible dynamics for a Klein Gordon scalar field. The prescription proposed for doing so involved viewing the spatial derivative part, A, of the wave operator as an operator on a certain L2 Hilbert space Script H and then defining a positive, self-adjoint operator on Script H by taking the Friedrichs extension (or other positive extension) of A. However, this analysis left open the possibility that there could be other inequivalent prescriptions of a completely different nature that might also yield satisfactory definitions of the dynamics of a scalar field. We show here that this is not the case. Specifically, we show that if the dynamics agrees locally with the dynamics defined by the wave equation, if it admits a suitable conserved energy and if it satisfies certain other specified conditions, then it must correspond to the dynamics defined by choosing some positive, self-adjoint extension of A on Script H. Thus, subject to our requirements, the previously given prescription is the only possible way of defining the dynamics of a scalar field in a static, non-globally-hyperbolic, spacetime. In a subsequent paper, this result will be applied to the analysis of scalar, electromagnetic and gravitational perturbations of anti-de Sitter spacetime. By doing so, we will determine all possible choices of boundary conditions at infinity in anti-de Sitter spacetime that give rise to sensible dynamics.

  16. Compaction behavior of isomalt after roll compaction.

    PubMed

    Quodbach, Julian; Mosig, Johanna; Kleinebudde, Peter

    2012-01-01

    The suitability of the new isomalt grade galenIQ™ 801 for dry granulation and following tableting is evaluated in this study. Isomalt alone, as well as a blend of equal parts with dibasic calcium phosphate, is roll compacted and tableted. Particle size distribution and flowability of the granules and friability and disintegration time of the tablets are determined. Tensile strength of tablets is related to the specific compaction force during roll compaction and the tableting force. In all cases, the tensile strength increases with raising tableting forces. The specific compaction force has a different influence. For isomalt alone the tensile strength is highest for tablets made from granules prepared at 2 kN/cm and 6 kN/cm and decreases at higher values, i.e., >10 kN/cm. Tensile strength of the blend tablets is almost one third lower compared to the strongest tablets of pure isomalt. Friability of pure isomalt tablets is above the limit. Disintegration time is longest when the tensile strength is at its maximum and decreases with higher porosity and lower tensile strengths. Isomalt proves to be suitable for tableting after roll compaction. Even though the capacity as a binder might not be as high as of other excipients, it is a further alternative for the formulation scientist. PMID:24300366

  17. Compaction Behavior of Isomalt after Roll Compaction

    PubMed Central

    Quodbach, Julian; Mosig, Johanna; Kleinebudde, Peter

    2012-01-01

    The suitability of the new isomalt grade galenIQ™ 801 for dry granulation and following tableting is evaluated in this study. Isomalt alone, as well as a blend of equal parts with dibasic calcium phosphate, is roll compacted and tableted. Particle size distribution and flowability of the granules and friability and disintegration time of the tablets are determined. Tensile strength of tablets is related to the specific compaction force during roll compaction and the tableting force. In all cases, the tensile strength increases with raising tableting forces. The specific compaction force has a different influence. For isomalt alone the tensile strength is highest for tablets made from granules prepared at 2 kN/cm and 6 kN/cm and decreases at higher values, i.e., >10 kN/cm. Tensile strength of the blend tablets is almost one third lower compared to the strongest tablets of pure isomalt. Friability of pure isomalt tablets is above the limit. Disintegration time is longest when the tensile strength is at its maximum and decreases with higher porosity and lower tensile strengths. Isomalt proves to be suitable for tableting after roll compaction. Even though the capacity as a binder might not be as high as of other excipients, it is a further alternative for the formulation scientist. PMID:24300366

  18. A simple hyperbolic model for communication in parallel processing environments

    NASA Technical Reports Server (NTRS)

    Stoica, Ion; Sultan, Florin; Keyes, David

    1994-01-01

    We introduce a model for communication costs in parallel processing environments called the 'hyperbolic model,' which generalizes two-parameter dedicated-link models in an analytically simple way. Dedicated interprocessor links parameterized by a latency and a transfer rate that are independent of load are assumed by many existing communication models; such models are unrealistic for workstation networks. The communication system is modeled as a directed communication graph in which terminal nodes represent the application processes that initiate the sending and receiving of the information and in which internal nodes, called communication blocks (CBs), reflect the layered structure of the underlying communication architecture. The direction of graph edges specifies the flow of the information carried through messages. Each CB is characterized by a two-parameter hyperbolic function of the message size that represents the service time needed for processing the message. The parameters are evaluated in the limits of very large and very small messages. Rules are given for reducing a communication graph consisting of many to an equivalent two-parameter form, while maintaining an approximation for the service time that is exact in both large and small limits. The model is validated on a dedicated Ethernet network of workstations by experiments with communication subprograms arising in scientific applications, for which a tight fit of the model predictions with actual measurements of the communication and synchronization time between end processes is demonstrated. The model is then used to evaluate the performance of two simple parallel scientific applications from partial differential equations: domain decomposition and time-parallel multigrid. In an appropriate limit, we also show the compatibility of the hyperbolic model with the recently proposed LogP model.

  19. Quantum error correcting codes and 4-dimensional arithmetic hyperbolic manifolds

    SciTech Connect

    Guth, Larry; Lubotzky, Alexander

    2014-08-15

    Using 4-dimensional arithmetic hyperbolic manifolds, we construct some new homological quantum error correcting codes. They are low density parity check codes with linear rate and distance n{sup ε}. Their rate is evaluated via Euler characteristic arguments and their distance using Z{sub 2}-systolic geometry. This construction answers a question of Zémor [“On Cayley graphs, surface codes, and the limits of homological coding for quantum error correction,” in Proceedings of Second International Workshop on Coding and Cryptology (IWCC), Lecture Notes in Computer Science Vol. 5557 (2009), pp. 259–273], who asked whether homological codes with such parameters could exist at all.

  20. Quantum error correcting codes and 4-dimensional arithmetic hyperbolic manifolds

    NASA Astrophysics Data System (ADS)

    Guth, Larry; Lubotzky, Alexander

    2014-08-01

    Using 4-dimensional arithmetic hyperbolic manifolds, we construct some new homological quantum error correcting codes. They are low density parity check codes with linear rate and distance nɛ. Their rate is evaluated via Euler characteristic arguments and their distance using {Z}_2-systolic geometry. This construction answers a question of Zémor ["On Cayley graphs, surface codes, and the limits of homological coding for quantum error correction," in Proceedings of Second International Workshop on Coding and Cryptology (IWCC), Lecture Notes in Computer Science Vol. 5557 (2009), pp. 259-273], who asked whether homological codes with such parameters could exist at all.

  1. Parabolic Perturbation of a Nonlinear Hyperbolic Problem Arising in Physiology

    NASA Astrophysics Data System (ADS)

    Colli, P.; Grasselli, M.

    We study a transport-diffusion initial value problem where the diffusion codlicient is "small" and the transport coefficient is a time function depending on the solution in a nonlinear and nonlocal way. We show the existence and the uniqueness of a weak solution of this problem. Moreover we discuss its asymptotic behaviour as the diffusion coefficient goes to zero, obtaining a well-posed first-order nonlinear hyperbolic problem. These problems arise from mathematical models of muscle contraction in the framework of the sliding filament theory.

  2. Hyperbolic Position Location Estimation in the Multipath Propagation Environment

    NASA Astrophysics Data System (ADS)

    Stefański, Jacek

    The efficiency analysis a hyperbolic position location estimation in the multipath propagation environment in the wideband code division multiple access (WCDMA) interface was presented. Four, the most popular methods: Chan’s [1], Foy’s [2], Fang’s [3] and Friedlander’s [4] were considered. These algorithms enable the calculation of the geographical position of a mobile station (MS) using the time differences of arrival (TDOA) between several base stations (BS) and MS. The simulation model is outlined and simulation results are presented.

  3. Hyperbolicity of scalar-tensor theories of gravity

    SciTech Connect

    Salgado, Marcelo; Martinez del Rio, David; Alcubierre, Miguel; Nunez, Dario

    2008-05-15

    Two first order strongly hyperbolic formulations of scalar-tensor theories of gravity allowing nonminimal couplings (Jordan frame) are presented along the lines of the 3+1 decomposition of spacetime. One is based on the Bona-Masso formulation, while the other one employs a conformal decomposition similar to that of Baumgarte-Shapiro-Shibata-Nakamura. A modified Bona-Masso slicing condition adapted to the scalar-tensor theory is proposed for the analysis. This study confirms that the scalar-tensor theory has a well-posed Cauchy problem even when formulated in the Jordan frame.

  4. Hyperbolic systems of equations posed on erroneous curved domains

    NASA Astrophysics Data System (ADS)

    Nordström, Jan; Nikkar, Samira

    2016-03-01

    The effect of an inaccurate geometry description on the solution accuracy of a hyperbolic problem is discussed. The inaccurate geometry can for example come from an imperfect CAD system, a faulty mesh generator, bad measurements or simply a misconception. We show that inaccurate geometry descriptions might lead to the wrong wave speeds, a misplacement of the boundary conditions, to the wrong boundary operator and a mismatch of boundary data. The errors caused by an inaccurate geometry description may affect the solution more than the accuracy of the specific discretization techniques used. In extreme cases, the order of accuracy goes to zero. Numerical experiments corroborate the theoretical results.

  5. Selective radiative heating of nanostructures using hyperbolic metamaterials

    SciTech Connect

    Ding, Ding; Minnich, Austin J

    2015-01-01

    Hyperbolic metamaterials (HMM) are of great interest due to their ability to break the diffraction limit for imaging and enhance near-field radiative heat transfer. Here we demonstrate that an annular, transparent HMM enables selective heating of a sub-wavelength plasmonic nanowire by controlling the angular mode number of a plasmonic resonance. A nanowire emitter, surrounded by an HMM, appears dark to incoming radiation from an adjacent nanowire emitter unless the second emitter is surrounded by an identical lens such that the wavelength and angular mode of the plasmonic resonance match. Our result can find applications in radiative thermal management.

  6. Hyperbolic umbilic diffraction catastrophe and rainbow scattering from spheroidal drops

    NASA Technical Reports Server (NTRS)

    Marston, P. L.; Trinh, E. H.

    1984-01-01

    Short-wavelength scattering from drops whose shapes closely approximate that of an oblate spheroid with a vertical short or symmetry axis have been studied. The drops were illuminated by a horizontally propagating gaussian beam with a wavelength of 633 nm. The drops were observed to scatter in the horizontal rainbow region with patterns like those of hyperbolic-umblic (classification D4(+)) diffraction catastrophes. Visible D4(+) diffraction patterns observed previously include light transmitted by frosted glass surfaces and by liquid lenses clinging to tilted glass plates.

  7. Compact plasma accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E. (Inventor)

    2004-01-01

    A compact plasma accelerator having components including a cathode electron source, an anodic ionizing gas source, and a magnetic field that is cusped. The components are held by an electrically insulating body having a central axis, a top axial end, and a bottom axial end. The cusped magnetic field is formed by a cylindrical magnet having an axis of rotation that is the same as the axis of rotation of the insulating body, and magnetized with opposite poles at its two axial ends; and an annular magnet coaxially surrounding the cylindrical magnet, magnetized with opposite poles at its two axial ends such that a top axial end has a magnetic polarity that is opposite to the magnetic polarity of a top axial end of the cylindrical magnet. The ionizing gas source is a tubular plenum that has been curved into a substantially annular shape, positioned above the top axial end of the annular magnet such that the plenum is centered in a ring-shaped cusp of the magnetic field generated by the magnets. The plenum has one or more capillary-like orifices spaced around its top such that an ionizing gas supplied through the plenum is sprayed through the one or more orifices. The plenum is electrically conductive and is positively charged relative to the cathode electron source such that the plenum functions as the anode; and the cathode is positioned above and radially outward relative to the plenum.

  8. Compact Doppler magnetograph

    NASA Astrophysics Data System (ADS)

    Ruzmaikin, Alexander; Moynihan, Philip I.; Vaughan, Arthur H.; Cacciani, Alessandro

    1998-11-01

    We designed a low-cost flight instrument that images the full solar disk through two narrow band filters at the red nd blue 'wings' of the solar potassium absorption line. The images are produced on a 1024 X 1024 charge-coupled device with a resolution of 2 arcsec per pixel. Four filtergrams taken in a very short time at both wings in the left and right states of circular polarization are used to yield a Dopplergram and a magnetogram simultaneously. The noise-equivalent velocity associated with each pixel is less than 3 m/s. The measured signal is linearly proportional to the velocity in the range +/- 4000 m/s. The range of magnetic fields is from 3 to 3000 Gauss. The optical system of the instrument is simple and easily aligned. With a pixel size of 12 micrometers , the effective focal length is 126 cm. A Raleigh resolution limit of 4 arcsec is achieved with a 5-cm entrance apertures, providing an f/25 focal ratio. The foreoptic is a two-component telephoto lens serving to limit the overall optical length to 89 cm or less. The mass of the instrument is 14 kg. the power required is less than 30 Watts. The Compact Doppler Magnetograph can be used in space mission with severe mass and power requirements. It can also be effectively used for ground-based observations: large telescope, dome or other observatory facilities are not required.

  9. Probability Weighting Functions Derived from Hyperbolic Time Discounting: Psychophysical Models and Their Individual Level Testing

    PubMed Central

    Takemura, Kazuhisa; Murakami, Hajime

    2016-01-01

    A probability weighting function (w(p)) is considered to be a nonlinear function of probability (p) in behavioral decision theory. This study proposes a psychophysical model of probability weighting functions derived from a hyperbolic time discounting model and a geometric distribution. The aim of the study is to show probability weighting functions from the point of view of waiting time for a decision maker. Since the expected value of a geometrically distributed random variable X is 1/p, we formulized the probability weighting function of the expected value model for hyperbolic time discounting as w(p) = (1 − k log p)−1. Moreover, the probability weighting function is derived from Loewenstein and Prelec's (1992) generalized hyperbolic time discounting model. The latter model is proved to be equivalent to the hyperbolic-logarithmic weighting function considered by Prelec (1998) and Luce (2001). In this study, we derive a model from the generalized hyperbolic time discounting model assuming Fechner's (1860) psychophysical law of time and a geometric distribution of trials. In addition, we develop median models of hyperbolic time discounting and generalized hyperbolic time discounting. To illustrate the fitness of each model, a psychological experiment was conducted to assess the probability weighting and value functions at the level of the individual participant. The participants were 50 university students. The results of individual analysis indicated that the expected value model of generalized hyperbolic discounting fitted better than previous probability weighting decision-making models. The theoretical implications of this finding are discussed. PMID:27303338

  10. Beautiful math, part 3: hyperbolic aesthetic patterns based on conformal mappings.

    PubMed

    Ouyang, Peichang; Chung, Kwokwai

    2014-01-01

    This third installment of the Beautiful Math articles considers the visualization of aesthetic patterns with hyperbolic-triangle-group symmetries. A flexible form of invariant mappings contributes to a simple, efficient way to generate hyperbolic patterns. Combined with conformal mappings, this method can yield an abundance of exotic patterns. PMID:24808201

  11. Probability Weighting Functions Derived from Hyperbolic Time Discounting: Psychophysical Models and Their Individual Level Testing.

    PubMed

    Takemura, Kazuhisa; Murakami, Hajime

    2016-01-01

    A probability weighting function (w(p)) is considered to be a nonlinear function of probability (p) in behavioral decision theory. This study proposes a psychophysical model of probability weighting functions derived from a hyperbolic time discounting model and a geometric distribution. The aim of the study is to show probability weighting functions from the point of view of waiting time for a decision maker. Since the expected value of a geometrically distributed random variable X is 1/p, we formulized the probability weighting function of the expected value model for hyperbolic time discounting as w(p) = (1 - k log p)(-1). Moreover, the probability weighting function is derived from Loewenstein and Prelec's (1992) generalized hyperbolic time discounting model. The latter model is proved to be equivalent to the hyperbolic-logarithmic weighting function considered by Prelec (1998) and Luce (2001). In this study, we derive a model from the generalized hyperbolic time discounting model assuming Fechner's (1860) psychophysical law of time and a geometric distribution of trials. In addition, we develop median models of hyperbolic time discounting and generalized hyperbolic time discounting. To illustrate the fitness of each model, a psychological experiment was conducted to assess the probability weighting and value functions at the level of the individual participant. The participants were 50 university students. The results of individual analysis indicated that the expected value model of generalized hyperbolic discounting fitted better than previous probability weighting decision-making models. The theoretical implications of this finding are discussed. PMID:27303338

  12. ACOUSTIC COMPACTION LAYER DETECTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The depth and strength of compacted layers in fields have been determined traditionally using the ASAE standardized cone penetrometer method. However, an on-the-go method would be much faster and much less labor intensive. The soil measurement system described here attempts to locate the compacted...

  13. Hyperbolic phonon-polaritons in boron nitride for near-field optical imaging and focusing

    NASA Astrophysics Data System (ADS)

    Li, Peining; Lewin, Martin; Kretinin, Andrey V.; Caldwell, Joshua D.; Novoselov, Kostya S.; Taniguchi, Takashi; Watanabe, Kenji; Gaussmann, Fabian; Taubner, Thomas

    2015-06-01

    Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength dependent propagation angle of hyperbolic phonon polaritons. With advanced infrared nanoimaging techniques and state-of-art mid-infrared laser sources, we have succeeded in demonstrating and visualizing these unexpected phenomena in both Type I and Type II hyperbolic conditions, with both occurring naturally within hexagonal boron nitride. These efforts have provided a full and intuitive physical picture for the understanding of the role of hyperbolic phonon polaritons in near-field optical imaging, guiding, and focusing applications.

  14. Hyperbolic phonon-polaritons in boron nitride for near-field optical imaging and focusing.

    PubMed

    Li, Peining; Lewin, Martin; Kretinin, Andrey V; Caldwell, Joshua D; Novoselov, Kostya S; Taniguchi, Takashi; Watanabe, Kenji; Gaussmann, Fabian; Taubner, Thomas

    2015-01-01

    Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength dependent propagation angle of hyperbolic phonon polaritons. With advanced infrared nanoimaging techniques and state-of-art mid-infrared laser sources, we have succeeded in demonstrating and visualizing these unexpected phenomena in both Type I and Type II hyperbolic conditions, with both occurring naturally within hexagonal boron nitride. These efforts have provided a full and intuitive physical picture for the understanding of the role of hyperbolic phonon polaritons in near-field optical imaging, guiding, and focusing applications. PMID:26112474

  15. Hyperbolic phonon-polaritons in boron nitride for near-field optical imaging and focusing

    PubMed Central

    Li, Peining; Lewin, Martin; Kretinin, Andrey V.; Caldwell, Joshua D.; Novoselov, Kostya S.; Taniguchi, Takashi; Watanabe, Kenji; Gaussmann, Fabian; Taubner, Thomas

    2015-01-01

    Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength dependent propagation angle of hyperbolic phonon polaritons. With advanced infrared nanoimaging techniques and state-of-art mid-infrared laser sources, we have succeeded in demonstrating and visualizing these unexpected phenomena in both Type I and Type II hyperbolic conditions, with both occurring naturally within hexagonal boron nitride. These efforts have provided a full and intuitive physical picture for the understanding of the role of hyperbolic phonon polaritons in near-field optical imaging, guiding, and focusing applications. PMID:26112474

  16. Generating Hyperbolic Singularities in Semitoric Systems Via Hopf Bifurcations

    NASA Astrophysics Data System (ADS)

    Dullin, Holger R.; Pelayo, Álvaro

    2016-06-01

    Let (M,Ω ) be a connected symplectic 4-manifold and let F=(J,H) :M→ {R}^2 be a completely integrable system on M with only non-degenerate singularities. Assume that F does not have singularities with hyperbolic blocks and that p_1,ldots ,p_n are the focus-focus singularities of F. For each subset S={i_1,ldots ,i_j}, we will show how to modify F locally around any p_i, i in S, in order to create a new integrable system widetilde{F}=(J, widetilde{H}) :M → {R}^2 such that its classical spectrum widetilde{F}(M) contains j smooth curves of singular values corresponding to non-degenerate transversally hyperbolic singularities of widetilde{F}. Moreover the focus-focus singularities of widetilde{F} are precisely p_i, i in {1,ldots ,n} setminus S. The proof is based on Eliasson's linearization theorem for non-degenerate singularities, and properties of the Hamiltonian Hopf bifurcation.

  17. Realization of mid-infrared graphene hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Chang, You-Chia; Liu, Che-Hung; Liu, Chang-Hua; Zhang, Siyuan; Marder, Seth R.; Narimanov, Evgenii E.; Zhong, Zhaohui; Norris, Theodore B.

    2016-02-01

    While metal is the most common conducting constituent element in the fabrication of metamaterials, graphene provides another useful building block, that is, a truly two-dimensional conducting sheet whose conductivity can be controlled by doping. Here we report the experimental realization of a multilayer structure of alternating graphene and Al2O3 layers, a structure similar to the metal-dielectric multilayers commonly used in creating visible wavelength hyperbolic metamaterials. Chemical vapour deposited graphene rather than exfoliated or epitaxial graphene is used, because layer transfer methods are easily applied in fabrication. We employ a method of doping to increase the layer conductivity, and our analysis shows that the doped chemical vapour deposited graphene has good optical properties in the mid-infrared range. We therefore design the metamaterial for mid-infrared operation; our characterization with an infrared ellipsometer demonstrates that the metamaterial experiences an optical topological transition from elliptic to hyperbolic dispersion at a wavelength of 4.5 μm.

  18. Realization of mid-infrared graphene hyperbolic metamaterials

    PubMed Central

    Chang, You-Chia; Liu, Che-Hung; Liu, Chang-Hua; Zhang, Siyuan; Marder, Seth R.; Narimanov, Evgenii E.; Zhong, Zhaohui; Norris, Theodore B.

    2016-01-01

    While metal is the most common conducting constituent element in the fabrication of metamaterials, graphene provides another useful building block, that is, a truly two-dimensional conducting sheet whose conductivity can be controlled by doping. Here we report the experimental realization of a multilayer structure of alternating graphene and Al2O3 layers, a structure similar to the metal-dielectric multilayers commonly used in creating visible wavelength hyperbolic metamaterials. Chemical vapour deposited graphene rather than exfoliated or epitaxial graphene is used, because layer transfer methods are easily applied in fabrication. We employ a method of doping to increase the layer conductivity, and our analysis shows that the doped chemical vapour deposited graphene has good optical properties in the mid-infrared range. We therefore design the metamaterial for mid-infrared operation; our characterization with an infrared ellipsometer demonstrates that the metamaterial experiences an optical topological transition from elliptic to hyperbolic dispersion at a wavelength of 4.5 μm. PMID:26843149

  19. Adaptive aberration correction using a triode hyperbolic electron mirror.

    PubMed

    Fitzgerald, J P S; Word, R C; Könenkamp, R

    2011-01-01

    A converging electron mirror can be used to compensate spherical and chromatic aberrations in an electron microscope. This paper presents an analytical solution to a novel triode (three electrode) hyperbolic mirror as an improvement to the well-known diode (two electrode) hyperbolic mirror for aberration correction. A weakness of the diode mirror is a lack of flexibility in changing the chromatic and spherical aberration coefficients independently without changes in the mirror geometry. In order to remove this limitation, a third electrode can be added. We calculate the optical properties of the resulting triode mirror analytically on the basis of a simple model field distribution. We present the optical properties-the object/image distance, z(0), and the coefficients of spherical and chromatic aberration, C(s) and C(c), of both mirror types from an analysis of electron trajectories in the mirror field. From this analysis, we demonstrate that while the properties of both designs are similar, the additional parameters in the triode mirror improve the range of aberration that can be corrected. The triode mirror is also able to provide a dynamic adjustment range of chromatic aberration for fixed spherical aberration and focal length, or any permutation of these three parameters. While the dynamic range depends on the values of aberration correction needed, a nominal 10% tuning range is possible for most configurations accompanied by less than 1% change in the other two properties. PMID:21930022

  20. Strategy Guideline: Compact Air Distribution Systems

    SciTech Connect

    Burdick, A.

    2013-06-01

    This Strategy Guideline discusses the benefits and challenges of using a compact air distribution system to handle the reduced loads and reduced air volume needed to condition the space within an energy efficient home. Traditional systems sized by 'rule of thumb' (i.e., 1 ton of cooling per 400 ft2 of floor space) that 'wash' the exterior walls with conditioned air from floor registers cannot provide appropriate air mixing and moisture removal in low-load homes. A compact air distribution system locates the HVAC equipment centrally with shorter ducts run to interior walls, and ceiling supply outlets throw the air toward the exterior walls along the ceiling plane; alternatively, high sidewall supply outlets throw the air toward the exterior walls. Potential drawbacks include resistance from installing contractors or code officials who are unfamiliar with compact air distribution systems, as well as a lack of availability of low-cost high sidewall or ceiling supply outlets to meet the low air volumes with good throw characteristics. The decision criteria for a compact air distribution system must be determined early in the whole-house design process, considering both supply and return air design. However, careful installation of a compact air distribution system can result in lower material costs from smaller equipment, shorter duct runs, and fewer outlets; increased installation efficiencies, including ease of fitting the system into conditioned space; lower loads on a better balanced HVAC system, and overall improved energy efficiency of the home.

  1. Compact Radiometers Expand Climate Knowledge

    NASA Technical Reports Server (NTRS)

    2010-01-01

    To gain a better understanding of Earth's water, energy, and carbon cycles, NASA plans to embark on the Soil Moisture Active and Passive mission in 2015. To prepare, Goddard Space Flight Center provided Small Business Innovation Research (SBIR) funding to ProSensing Inc., of Amherst, Massachusetts, to develop a compact ultrastable radiometer for sea surface salinity and soil moisture mapping. ProSensing incorporated small, low-cost, high-performance elements into just a few circuit boards and now offers two lightweight radiometers commercially. Government research agencies, university research groups, and large corporations around the world are using the devices for mapping soil moisture, ocean salinity, and wind speed.

  2. Compaction properties of isomalt.

    PubMed

    Bolhuis, Gerad K; Engelhart, Jeffrey J P; Eissens, Anko C

    2009-08-01

    Although other polyols have been described extensively as filler-binders in direct compaction of tablets, the polyol isomalt is rather unknown as pharmaceutical excipient, in spite of its description in all the main pharmacopoeias. In this paper the compaction properties of different types of ispomalt were studied. The types used were the standard product sieved isomalt, milled isomalt and two types of agglomerated isomalt with a different ratio between 6-O-alpha-d-glucopyranosyl-d-sorbitol (GPS) and 1-O-alpha-d-glucopyranosyl-d-mannitol dihydrate (GPM). Powder flow properties, specific surface area and densities of the different types were investigated. Compactibility was investigated by compression of the tablets on a compaction simulator, simulating the compression on high-speed tabletting machines. Lubricant sensitivity was measured by compressing unlubricated tablets and tablets lubricated with 1% magnesium stearate on an instrumented hydraulic press. Sieved isomalt had excellent flow properties but the compactibility was found to be poor whereas the lubricant sensitivity was high. Milling resulted in both a strong increase in compactibility as an effect of the higher surface area for bonding and a decrease in lubricant sensitivity as an effect of the higher surface area to be coated with magnesium stearate. However, the flow properties of milled isomalt were too bad for use as filler-binder in direct compaction. Just as could be expected, agglomeration of milled isomalt by fluid bed agglomeration improved flowability. The good compaction properties and the low lubricant sensitivity were maintained. This effect is caused by an early fragmentation of the agglomerated material during the compaction process, producing clean, lubricant-free particles and a high surface for bonding. The different GPS/GPM ratios of the agglomerated isomalt types studied had no significant effect on the compaction properties. PMID:19327398

  3. Stabilization of compactible waste

    SciTech Connect

    Franz, E.M.; Heiser, J.H. III; Colombo, P.

    1990-09-01

    This report summarizes the results of series of experiments performed to determine the feasibility of stabilizing compacted or compactible waste with polymers. The need for this work arose from problems encountered at disposal sites attributed to the instability of this waste in disposal. These studies are part of an experimental program conducted at Brookhaven National Laboratory (BNL) investigating methods for the improved solidification/stabilization of DOE low-level wastes. The approach taken in this study was to perform a series of survey type experiments using various polymerization systems to find the most economical and practical method for further in-depth studies. Compactible dry bulk waste was stabilized with two different monomer systems: styrene-trimethylolpropane trimethacrylate (TMPTMA) and polyester-styrene, in laboratory-scale experiments. Stabilization was accomplished by wetting or soaking compactible waste (before or after compaction) with monomers, which were subsequently polymerized. Three stabilization methods are described. One involves the in-situ treatment of compacted waste with monomers in which a vacuum technique is used to introduce the binder into the waste. The second method involves the alternate placement and compaction of waste and binder into a disposal container. In the third method, the waste is treated before compaction by wetting the waste with the binder using a spraying technique. A series of samples stabilized at various binder-to-waste ratios were evaluated through water immersion and compression testing. Full-scale studies were conducted by stabilizing two 55-gallon drums of real compacted waste. The results of this preliminary study indicate that the integrity of compacted waste forms can be readily improved to ensure their long-term durability in disposal environments. 9 refs., 10 figs., 2 tabs.

  4. A higher-order conservation element solution element method for solving hyperbolic differential equations on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Bilyeu, David

    This dissertation presents an extension of the Conservation Element Solution Element (CESE) method from second- to higher-order accuracy. The new method retains the favorable characteristics of the original second-order CESE scheme, including (i) the use of the space-time integral equation for conservation laws, (ii) a compact mesh stencil, (iii) the scheme will remain stable up to a CFL number of unity, (iv) a fully explicit, time-marching integration scheme, (v) true multidimensionality without using directional splitting, and (vi) the ability to handle two- and three-dimensional geometries by using unstructured meshes. This algorithm has been thoroughly tested in one, two and three spatial dimensions and has been shown to obtain the desired order of accuracy for solving both linear and non-linear hyperbolic partial differential equations. The scheme has also shown its ability to accurately resolve discontinuities in the solutions. Higher order unstructured methods such as the Discontinuous Galerkin (DG) method and the Spectral Volume (SV) methods have been developed for one-, two- and three-dimensional application. Although these schemes have seen extensive development and use, certain drawbacks of these methods have been well documented. For example, the explicit versions of these two methods have very stringent stability criteria. This stability criteria requires that the time step be reduced as the order of the solver increases, for a given simulation on a given mesh. The research presented in this dissertation builds upon the work of Chang, who developed a fourth-order CESE scheme to solve a scalar one-dimensional hyperbolic partial differential equation. The completed research has resulted in two key deliverables. The first is a detailed derivation of a high-order CESE methods on unstructured meshes for solving the conservation laws in two- and three-dimensional spaces. The second is the code implementation of these numerical methods in a computer code. For

  5. A new spectral difference method using hierarchical polynomial bases for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Liang, Xie; Min, Xu; Bin, Zhang; Zihua, Qiu

    2015-03-01

    To solve hyperbolic conservation laws, a new method is developed based on the spectral difference (SD) algorithm. The new scheme adopts hierarchical polynomials to represent the solution in each cell instead of Lagrange interpolation polynomials used by the original one. The degrees of freedom (DOFs) of the present scheme are the coefficients of these polynomials, which do not represent the states at the solution points like the original method. Therefore, the solution points defined in the original SD scheme are discarded, while the flux points are preserved to construct a Lagrange interpolation polynomial to approximate flux function in each cell. To update the DOFs, differential operators are applied to the governing equation as well as the Lagrange interpolation polynomial of flux function to evaluate first and higher order derivatives of both solution and flux at the centroid of the cell. The stability property of the current scheme is proved to be the same as the original SD method when the same solution space is adopted. One dimensional methods are always stable by the use of zeros of Legendre polynomials as inner flux points. For two dimensional problems, the introduction of Raviart-Thomas spaces for the interpolation of flux function proves stable schemes for triangles. Accuracy studies are performed with one- and two-dimensional problems. p-Multigrid algorithm is implemented with orthogonal hierarchical bases. The results verify the high efficiency and low memory requirements of implementation of p-multigrid algorithm with the proposed scheme.

  6. Resin-Impregnated Carbon Ablator: A New Ablative Material for Hyperbolic Entry Speeds

    NASA Technical Reports Server (NTRS)

    Esper, Jaime; Lengowski, Michael

    2012-01-01

    Ablative materials are required to protect a space vehicle from the extreme temperatures encountered during the most demanding (hyperbolic) atmospheric entry velocities, either for probes launched toward other celestial bodies, or coming back to Earth from deep space missions. To that effect, the resin-impregnated carbon ablator (RICA) is a high-temperature carbon/phenolic ablative thermal protection system (TPS) material designed to use modern and commercially viable components in its manufacture. Heritage carbon/phenolic ablators intended for this use rely on materials that are no longer in production (i.e., Galileo, Pioneer Venus); hence the development of alternatives such as RICA is necessary for future NASA planetary entry and Earth re-entry missions. RICA s capabilities were initially measured in air for Earth re-entry applications, where it was exposed to a heat flux of 14 MW/sq m for 22 seconds. Methane tests were also carried out for potential application in Saturn s moon Titan, with a nominal heat flux of 1.4 MW/sq m for up to 478 seconds. Three slightly different material formulations were manufactured and subsequently tested at the Plasma Wind Tunnel of the University of Stuttgart in Germany (PWK1) in the summer and fall of 2010. The TPS integrity was well preserved in most cases, and results show great promise.

  7. Fully discrete energy stable high order finite difference methods for hyperbolic problems in deforming domains

    NASA Astrophysics Data System (ADS)

    Nikkar, Samira; Nordström, Jan

    2015-06-01

    A time-dependent coordinate transformation of a constant coefficient hyperbolic system of equations which results in a variable coefficient system of equations is considered. By applying the energy method, well-posed boundary conditions for the continuous problem are derived. Summation-by-Parts (SBP) operators for the space and time discretization, together with a weak imposition of boundary and initial conditions using Simultaneously Approximation Terms (SATs) lead to a provable fully-discrete energy-stable conservative finite difference scheme. We show how to construct a time-dependent SAT formulation that automatically imposes boundary conditions, when and where they are required. We also prove that a uniform flow field is preserved, i.e. the Numerical Geometric Conservation Law (NGCL) holds automatically by using SBP-SAT in time and space. The developed technique is illustrated by considering an application using the linearized Euler equations: the sound generated by moving boundaries. Numerical calculations corroborate the stability and accuracy of the new fully discrete approximations.

  8. Stable and accurate hybrid finite volume methods based on pure convexity arguments for hyperbolic systems of conservation law

    NASA Astrophysics Data System (ADS)

    De Vuyst, Florian

    2004-01-01

    This exploratory work tries to present first results of a novel approach for the numerical approximation of solutions of hyperbolic systems of conservation laws. The objective is to define stable and "reasonably" accurate numerical schemes while being free from any upwind process and from any computation of derivatives or mean Jacobian matrices. That means that we only want to perform flux evaluations. This would be useful for "complicated" systems like those of two-phase models where solutions of Riemann problems are hard, see impossible to compute. For Riemann or Roe-like solvers, each fluid model needs the particular computation of the Jacobian matrix of the flux and the hyperbolicity property which can be conditional for some of these models makes the matrices be not R-diagonalizable everywhere in the admissible state space. In this paper, we rather propose some numerical schemes where the stability is obtained using convexity considerations. A certain rate of accuracy is also expected. For that, we propose to build numerical hybrid fluxes that are convex combinations of the second-order Lax-Wendroff scheme flux and the first-order modified Lax-Friedrichs scheme flux with an "optimal" combination rate that ensures both minimal numerical dissipation and good accuracy. The resulting scheme is a central scheme-like method. We will also need and propose a definition of local dissipation by convexity for hyperbolic or elliptic-hyperbolic systems. This convexity argument allows us to overcome the difficulty of nonexistence of classical entropy-flux pairs for certain systems. We emphasize the systematic feature of the method which can be fastly implemented or adapted to any kind of systems, with general analytical or data-tabulated equations of state. The numerical results presented in the paper are not superior to many existing state-of-the-art numerical methods for conservation laws such as ENO, MUSCL or central scheme of Tadmor and coworkers. The interest is rather

  9. Compact Translating-Head Magnetic Memories

    NASA Technical Reports Server (NTRS)

    Katti, Romney R.

    1992-01-01

    Stationary magnetic media stores information at densities up to 6.5 Gb/cm(Sup 2). High-density memory devices combine features of advanced rotating-disk magnetic recording and playback systems with compact two-axis high-acceleration linear actuators. New devices weigh less, occupy less space, and consume less power than disk and tape recorders.

  10. Compact Microwave Fourier Spectrum Analyzer

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry

    2009-01-01

    A compact photonic microwave Fourier spectrum analyzer [a Fourier-transform microwave spectrometer, (FTMWS)] with no moving parts has been proposed for use in remote sensing of weak, natural microwave emissions from the surfaces and atmospheres of planets to enable remote analysis and determination of chemical composition and abundances of critical molecular constituents in space. The instrument is based on a Bessel beam (light modes with non-zero angular momenta) fiber-optic elements. It features low power consumption, low mass, and high resolution, without a need for any cryogenics, beyond what is achievable by the current state-of-the-art in space instruments. The instrument can also be used in a wide-band scatterometer mode in active radar systems.

  11. Compact Microscope Imaging System Developed

    NASA Technical Reports Server (NTRS)

    McDowell, Mark

    2001-01-01

    The Compact Microscope Imaging System (CMIS) is a diagnostic tool with intelligent controls for use in space, industrial, medical, and security applications. The CMIS can be used in situ with a minimum amount of user intervention. This system, which was developed at the NASA Glenn Research Center, can scan, find areas of interest, focus, and acquire images automatically. Large numbers of multiple cell experiments require microscopy for in situ observations; this is only feasible with compact microscope systems. CMIS is a miniature machine vision system that combines intelligent image processing with remote control capabilities. The software also has a user-friendly interface that can be used independently of the hardware for post-experiment analysis. CMIS has potential commercial uses in the automated online inspection of precision parts, medical imaging, security industry (examination of currency in automated teller machines and fingerprint identification in secure entry locks), environmental industry (automated examination of soil/water samples), biomedical field (automated blood/cell analysis), and microscopy community. CMIS will improve research in several ways: It will expand the capabilities of MSD experiments utilizing microscope technology. It may be used in lunar and Martian experiments (Rover Robot). Because of its reduced size, it will enable experiments that were not feasible previously. It may be incorporated into existing shuttle orbiter and space station experiments, including glove-box-sized experiments as well as ground-based experiments.

  12. Compact microchannel system

    DOEpatents

    Griffiths, Stewart

    2003-09-30

    The present invention provides compact geometries for the layout of microchannel columns through the use of turns and straight channel segments. These compact geometries permit the use of long separation or reaction columns on a small microchannel substrate or, equivalently, permit columns of a fixed length to occupy a smaller substrate area. The new geometries are based in part on mathematical analyses that provide the minimum turn radius for which column performance in not degraded. In particular, we find that straight channel segments of sufficient length reduce the required minimum turn radius, enabling compact channel layout when turns and straight segments are combined. The compact geometries are obtained by using turns and straight segments in overlapped or nested arrangements to form pleated or coiled columns.

  13. Dark compact planets

    NASA Astrophysics Data System (ADS)

    Tolos, Laura; Schaffner-Bielich, Jürgen

    2015-12-01

    We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron-star matter and white-dwarf material. We consider non-self annihilating dark matter with an equation of state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses and radii from a few Km to few hundred Km for weakly interacting dark matter which are stabilized by the mutual presence of dark matter and compact star matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses and radii of few hundred Km. These objects could be detected by observing exoplanets with unusually small radii. Moreover, we find that the recently observed 2 M⊙ pulsars set limits on the amount of dark matter inside neutron stars which is, at most, 1 0-6 M⊙ .

  14. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging

    NASA Astrophysics Data System (ADS)

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-04-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques.

  15. Hyperbolic metamaterial antenna for second-harmonic generation tomography.

    PubMed

    Segovia, Paulina; Marino, Giuseppe; Krasavin, Alexey V; Olivier, Nicolas; Wurtz, Gregory A; Belov, Pavel A; Ginzburg, Pavel; Zayats, Anatoly V

    2015-11-30

    The detection and processing of information carried by evanescent field components are key elements for subwavelength optical microscopy as well as single molecule sensing applications. Here, we numerically demonstrate the potential of a hyperbolic medium in the design of an efficient metamaterial antenna enabling detection and tracking of a nonlinear object, with an otherwise hidden second-harmonic signature. The presence of the antenna provides 103-fold intensity enhancement of the second harmonic generation (SHG) from a nanoparticle through a metamaterial-assisted access to evanescent second-harmonic fields. Alternatively, the observation of SHG from the metamaterial itself can be used to detect and track a nanoparticle without a nonlinear response. The antenna allows an optical resolution of several nanometers in tracking the nanoparticle's location via observations of the far-field second-harmonic radiation pattern. PMID:26698705

  16. Absorbing boundary conditions for second-order hyperbolic equations

    NASA Technical Reports Server (NTRS)

    Jiang, Hong; Wong, Yau Shu

    1989-01-01

    A uniform approach to construct absorbing artificial boundary conditions for second-order linear hyperbolic equations is proposed. The nonlocal boundary condition is given by a pseudodifferential operator that annihilates travelling waves. It is obtained through the dispersion relation of the differential equation by requiring that the initial-boundary value problem admits the wave solutions travelling in one direction only. Local approximation of this global boundary condition yields an nth-order differential operator. It is shown that the best approximations must be in the canonical forms which can be factorized into first-order operators. These boundary conditions are perfectly absorbing for wave packets propagating at certain group velocities. A hierarchy of absorbing boundary conditions is derived for transonic small perturbation equations of unsteady flows. These examples illustrate that the absorbing boundary conditions are easy to derive, and the effectiveness is demonstrated by the numerical experiments.

  17. Non-oscillatory central differencing for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Nessyahu, Haim; Tadmor, Eitan

    1990-01-01

    Many of the recently developed high resolution schemes for hyperbolic conservation laws are based on upwind differencing. The building block for these schemes is the averaging of an appropriate Godunov solver; its time consuming part involves the field-by-field decomposition which is required in order to identify the direction of the wind. Instead, the use of the more robust Lax-Friedrichs (LxF) solver is proposed. The main advantage is simplicity: no Riemann problems are solved and hence field-by-field decompositions are avoided. The main disadvantage is the excessive numerical viscosity typical to the LxF solver. This is compensated for by using high-resolution MUSCL-type interpolants. Numerical experiments show that the quality of results obtained by such convenient central differencing is comparable with those of the upwind schemes.

  18. Non-oscillatory central differencing for hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Nessyahu, Haim; Tadmor, Eitan

    1988-01-01

    Many of the recently developed high resolution schemes for hyperbolic conservation laws are based on upwind differencing. The building block for these schemes is the averaging of an appropriate Godunov solver; its time consuming part involves the field-by-field decomposition which is required in order to identify the direction of the wind. Instead, the use of the more robust Lax-Friedrichs (LxF) solver is proposed. The main advantage is simplicity: no Riemann problems are solved and hence field-by-field decompositions are avoided. The main disadvantage is the excessive numerical viscosity typical to the LxF solver. This is compensated for by using high-resolution MUSCL-type interpolants. Numerical experiments show that the quality of results obtained by such convenient central differencing is comparable with those of the upwind schemes.

  19. Hyperbolic tangential function-based progressive addition lens design.

    PubMed

    Qiu, Gufeng; Cui, Xudong

    2015-12-10

    The diopter distribution is key to the successful design of a progressive addition lens. A hyperbolic tangential function is then introduced to describe well the desired diopter distribution on the lens. Simulation and fabrication show that the astigmia on the whole surface is very close to the addition, exhibiting superior performance than that of currently used high-order polynomials and cosine functions. Our investigations found that once the diopter distribution design is reasonable, both the direct and indirect methods of constructing a progressive addition lens can give consistent results. With this function we are able to effectively control the design of critical areas, the position, sizes of far-view and near-view zones, as well as the channel of the lens. This study would provide an efficient way to customize different progressive lenses not only for presbyopia, but also for anti-fatigue, office progressive usages, etc. PMID:26836863

  20. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging.

    PubMed

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-01-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques. PMID:27040762

  1. Nonlinear hyperbolic theory of thermal waves in metals

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E.; Choi, S. H.

    1975-01-01

    A closed-form solution for cylindrical thermal waves in metals is given based on the nonlinear hyperbolic system of energy-conservation and heat-flux relaxation equations. It is shown that heat released from a line source propagates radially outward with finite speed in the form of a thermal wave which exhibits a discontinuous wave front. Unique nonlinear thermal-wave solutions exist up to a critical amount of driving energy, i.e., for larger energy releases, the thermal flow becomes multivalued (occurrence of shock waves). By comparison, it is demonstrated that the parabolic thermal-wave theory gives, in general, a misleading picture of the profile and propagation of thermal waves and leads to physical (infinite speed of heat propagation) and mathematical (divergent energy integrals) difficulties. Attention is drawn to the importance of temporal heat-flux relaxation for the physical understanding of fast transient processes such as thermal waves and more general explosions and implosions.

  2. Absorbing boundary conditions for second-order hyperbolic equations

    NASA Technical Reports Server (NTRS)

    Jiang, Hong; Wong, Yau Shu

    1990-01-01

    A uniform approach to construct absorbing artificial boundary conditions for second-order linear hyperbolic equations is proposed. The nonlocal boundary condition is given by a pseudodifferential operator that annihilates travelling waves. It is obtained through the dispersion relation of the differential equation by requiring that the initial-boundary value problem admits the wave solutions travelling in one direction only. Local approximation of this global boundary condition yields an nth-order differential operator. It is shown that the best approximations must be in the canonical forms which can be factorized into first-order operators. These boundary conditions are perfectly absorbing for wave packets propagating at certain group velocities. A hierarchy of absorbing boundary conditions is derived for transonic small perturbation equations of unsteady flows. These examples illustrate that the absorbing boundary conditions are easy to derive, and the effectiveness is demonstrated by the numerical experiments.

  3. Parallel computation with adaptive methods for elliptic and hyperbolic systems

    SciTech Connect

    Benantar, M.; Biswas, R.; Flaherty, J.E.; Shephard, M.S.

    1990-01-01

    We consider the solution of two dimensional vector systems of elliptic and hyperbolic partial differential equations on a shared memory parallel computer. For elliptic problems, the spatial domain is discretized using a finite quadtree mesh generation procedure and the differential system is discretized by a finite element-Galerkin technique with a piecewise linear polynomial basis. Resulting linear algebraic systems are solved using the conjugate gradient technique with element-by-element and symmetric successive over-relaxation preconditioners. Stiffness matrix assembly and linear system solutions are processed in parallel with computations scheduled on noncontiguous quadrants of the tree in order to minimize process synchronization. Determining noncontiguous regions by coloring the regular finite quadtree structure is far simpler than coloring elements of the unstructured mesh that the finite quadtree procedure generates. We describe linear-time complexity coloring procedures that use six and eight colors.

  4. Quantum hyperbolic geometry in loop quantum gravity with cosmological constant

    NASA Astrophysics Data System (ADS)

    Dupuis, Maïté; Girelli, Florian

    2013-06-01

    Loop quantum gravity (LQG) is an attempt to describe the quantum gravity regime. Introducing a nonzero cosmological constant Λ in this context has been a standing problem. Other approaches, such as Chern-Simons gravity, suggest that quantum groups can be used to introduce Λ into the game. Not much is known when defining LQG with a quantum group. Tensor operators can be used to construct observables in any type of discrete quantum gauge theory with a classical/quantum gauge group. We illustrate this by constructing explicitly geometric observables for LQG defined with a quantum group and show for the first time that they encode a quantized hyperbolic geometry. This is a novel argument pointing out the usefulness of quantum groups as encoding a nonzero cosmological constant. We conclude by discussing how tensor operators provide the right formalism to unlock the LQG formulation with a nonzero cosmological constant.

  5. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging

    PubMed Central

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-01-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques. PMID:27040762

  6. A multiband perfect absorber based on hyperbolic metamaterials

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; ElKabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R.; Gurkan, Umut A.; Strangi, Giuseppe

    2016-01-01

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors. PMID:27188789

  7. Coupled sloshing in hyperbolic containers suspended as a bifilar pendulum

    NASA Astrophysics Data System (ADS)

    Turner, M. R.; Weidman, Patrick

    2016-08-01

    The coupled interaction between a sloshing fluid in a partially filled container suspended as a bifilar pendulum is investigated. The sloshing fluid has a free surface upon which waves are generated; this fluid contributes a restoring force to the container motion by its weight through the wire suspensions and the free-surface waves may either enhance or diminish the restoring force through hydrodynamic interaction with the container walls. Results are presented for inviscid irrotational sloshing in both a two-dimensional hyperbolic container and a three-dimensional hyperboloid container. Frequency results for the coupled system are presented for various pendulum lengths and fluid fill heights. It is found that for long pendulum lengths the container and the fluid oscillate in a synchronous motion when the vessel is released with typical experimental initial conditions, but for pendulum lengths below a given threshold the container and fluid oscillate asynchronously from the same initial condition.

  8. A multiband perfect absorber based on hyperbolic metamaterials.

    PubMed

    Sreekanth, Kandammathe Valiyaveedu; ElKabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R; Gurkan, Umut A; Strangi, Giuseppe

    2016-01-01

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors. PMID:27188789

  9. A multiband perfect absorber based on hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Sreekanth, Kandammathe Valiyaveedu; Elkabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R.; Gurkan, Umut A.; Strangi, Giuseppe

    2016-05-01

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors.

  10. Generalized -deformed correlation functions as spectral functions of hyperbolic geometry

    NASA Astrophysics Data System (ADS)

    Bonora, L.; Bytsenko, A. A.; Guimarães, M. E. X.

    2014-08-01

    We analyze the role of vertex operator algebra and 2d amplitudes from the point of view of the representation theory of infinite-dimensional Lie algebras, MacMahon and Ruelle functions. By definition p-dimensional MacMahon function, with , is the generating function of p-dimensional partitions of integers. These functions can be represented as amplitudes of a two-dimensional c = 1 CFT, and, as such, they can be generalized to . With some abuse of language we call the latter amplitudes generalized MacMahon functions. In this paper we show that generalized p-dimensional MacMahon functions can be rewritten in terms of Ruelle spectral functions, whose spectrum is encoded in the Patterson-Selberg function of three-dimensional hyperbolic geometry.

  11. Fifth international conference on hyperbolic problems -- theory, numerics, applications: Abstracts

    SciTech Connect

    1994-12-31

    The conference demonstrated that hyperbolic problems and conservation laws play an important role in many areas including industrial applications and the studying of elasto-plastic materials. Among the various topics covered in the conference, the authors mention: the big bang theory, general relativity, critical phenomena, deformation and fracture of solids, shock wave interactions, numerical simulation in three dimensions, the level set method, multidimensional Riemann problem, application of the front tracking in petroleum reservoir simulations, global solution of the Navier-Stokes equations in high dimensions, recent progress in granular flow, and the study of elastic plastic materials. The authors believe that the new ideas, tools, methods, problems, theoretical results, numerical solutions and computational algorithms presented or discussed at the conference will benefit the participants in their current and future research.

  12. Critical coupling with graphene-based hyperbolic metamaterials

    PubMed Central

    Xiang, Yuanjiang; Dai, Xiaoyu; Guo, Jun; Zhang, Han; Wen, Shuangchun; Tang, Dingyuan

    2014-01-01

    In order to effectively realize and control the critical coupling, a graphene-based hyperbolic metamaterial has been proposed to replace the absorbing thin film in the critically coupled resonance structure. Our calculations demonstrate that the critical coupling effect (near-perfect light absorption) can be achieved at the near-infrared wavelength by using this layered structure, while the critical coupling frequency can be tuned by varying the Fermi energy level of graphene sheets via electrostatic biasing. Moreover, we show that the critical coupling frequency can be tuned by changing the thickness of the dielectric or layer number of the graphene sheets in the unit cell of the graphene-dielectric HMM. The optimization performance has also been indicated, which may offer an opportunity towards the experimental designs of high efficient graphene based critical coupling devices. PMID:24970717

  13. Compact baby Skyrmions

    SciTech Connect

    Adam, C.; Klimas, P.; Sanchez-Guillen, J.; Wereszczynski, A.

    2009-11-15

    For the baby Skyrme model with a specific potential, compacton solutions, i.e., configurations with a compact support and parabolic approach to the vacuum, are derived. Specifically, in the nontopological sector, we find spinning Q-balls and Q-shells, as well as peakons. Moreover, we obtain compact baby skyrmions with nontrivial topological charge. All these solutions may form stable multisoliton configurations provided they are sufficiently separated.

  14. Verification of hyperbolicity for attractors of some mechanical systems with chaotic dynamics

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Sergey P.; Kruglov, Vyacheslav P.

    2016-03-01

    Computer verification of hyperbolicity is provided based on statistical analysis of the angles of intersection of stable and unstable manifolds for mechanical systems with hyperbolic attractors of Smale-Williams type: (i) a particle sliding on a plane under periodic kicks, (ii) interacting particles moving on two alternately rotating disks, and (iii) a string with parametric excitation of standing-wave patterns by a modulated pump. The examples are of interest as contributing to filling the hyperbolic theory of dynamical systems with physical content.

  15. Analytical solution to a non-autonomous second order differential equation with modified hyperbolic tangent function

    NASA Astrophysics Data System (ADS)

    Fernández-Guasti, M.

    2015-03-01

    The solution to a non-autonomous second order ordinary differential equation is presented. The real function, dependent on the differentiation variable, is a squared hyperbolic tangent function plus a term that involves the quotient of hyperbolic functions. This function varies from one limiting value to another without having any singularities. The solution is remarkably simple and involves only trigonometric and hyperbolic trigonometric functions. The solution is analyzed in the context of wave propagation in an inhomogeneous one-dimensional medium. The profile is shown to act as a perfect anti-reflection interface, providing a possible alternative route to the fabrication of reflectionless surfaces.

  16. Gauss Modular-Arithmetic Congruence = Signal X Noise PRODUCT: Clock-model Archimedes HYPERBOLICITY Centrality INEVITABILITY: Definition: Complexity= UTTER-SIMPLICITY: Natural-Philosophy UNITY SIMPLICITY Redux!!!

    NASA Astrophysics Data System (ADS)

    Kummer, E. E.; Siegel, Edward Carl-Ludwig

    2011-03-01

    Clock-model Archimedes [http://linkage.rockeller.edu/ wli/moved.8.04/ 1fnoise/ index. ru.html] HYPERBOLICITY inevitability throughout physics/pure-maths: Newton-law F=ma, Heisenberg and classical uncertainty-principle=Parseval/Plancherel-theorems causes FUZZYICS definition: (so miscalled) "complexity" = UTTER-SIMPLICITY!!! Watkins[www.secamlocal.ex.ac.uk/people/staff/mrwatkin/]-Hubbard[World According to Wavelets (96)-p.14!]-Franklin[1795]-Fourier[1795;1822]-Brillouin[1922] dual/inverse-space(k,w) analysis key to Fourier-unification in Archimedes hyperbolicity inevitability progress up Siegel cognition hierarchy-of-thinking (HoT): data-info.-know.-understand.-meaning-...-unity-simplicity = FUZZYICS!!! Frohlich-Mossbauer-Goldanskii-del Guidice [Nucl.Phys.B:251,375(85);275,185 (86)]-Young [arXiv-0705.4678y2, (5/31/07] theory of health/life=aqueous-electret/ ferroelectric protoplasm BEC = Archimedes-Siegel [Schrodinger Cent.Symp.(87); Symp.Fractals, MRS Fall Mtg.(89)-5-pprs] 1/w-"noise" Zipf-law power-spectrum hyperbolicity INEVITABILITY= Chi; Dirac delta-function limit w=0 concentration= BEC = Chi-Quong.

  17. A Compact Gas/Tungsten-Arc Welding Torch

    NASA Technical Reports Server (NTRS)

    Morgen, Gene E.

    1991-01-01

    Compact gas/tungsten-arc welding torch delivers 100-A current, yet used in confined spaces inaccessible to even smallest commercially available torch. Despite its extremely small size, torch contains all usual components and delivers high current.

  18. Variable thermal properties and thermal relaxation time in hyperbolic heat conduction

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Mcrae, D. Scott

    1989-01-01

    Numerical solutions were obtained for a finite slab with an applied surface heat flux at one boundary using both the hyperbolic (MacCormack's method) and parabolic (Crank-Nicolson method) heat conduction equations. The effects on the temperature distributions of varying density, specific heat, and thermal relaxation time were calculated. Each of these properties had an effect on the thermal front velocity (in the hyperbolic solution) as well as the temperatures in the medium. In the hyperbolic solutions, as the density or specific heat decreased with temperature, both the temperatures within the medium and the thermal front velocity increased. The value taken for the thermal relaxation time was found to determine the 'hyperbolicity' of the heat conduction model. The use of a time dependent relaxation time allowed for solutions where the thermal energy propagated as a high temperature wave initially, but approached a diffusion process more rapidly than was possible with a constant large relaxation time.

  19. Adaptive Inverse Hyperbolic Tangent Algorithm for Dynamic Contrast Adjustment in Displaying Scenes

    NASA Astrophysics Data System (ADS)

    Yu, Cheng-Yi; Ouyang, Yen-Chieh; Wang, Chuin-Mu; Chang, Chein-I.

    2010-12-01

    Contrast has a great influence on the quality of an image in human visual perception. A poorly illuminated environment can significantly affect the contrast ratio, producing an unexpected image. This paper proposes an Adaptive Inverse Hyperbolic Tangent (AIHT) algorithm to improve the display quality and contrast of a scene. Because digital cameras must maintain the shadow in a middle range of luminance that includes a main object such as a face, a gamma function is generally used for this purpose. However, this function has a severe weakness in that it decreases highlight contrast. To mitigate this problem, contrast enhancement algorithms have been designed to adjust contrast to tune human visual perception. The proposed AIHT determines the contrast levels of an original image as well as parameter space for different contrast types so that not only the original histogram shape features can be preserved, but also the contrast can be enhanced effectively. Experimental results show that the proposed algorithm is capable of enhancing the global contrast of the original image adaptively while extruding the details of objects simultaneously.

  20. Strictly hyperbolic models of co-current three-phase flow withgravity

    SciTech Connect

    Juanes, Ruben; Patzek, Tadeusz W.

    2002-11-18

    We study the character of the equations in the traditional formulation of one-dimensional immiscible three-phase flow with gravity, in the limit of negligible capillarity. We restrict our analysis to co-current flow required for a displacement process; in cases of mixed co-current and counter-current flow, capillarity effects cannot be dropped from the formulation. The model makes use of the classical multiphase extension of Darcy's equation. It is well known that, if relative permeabilities are taken as fixed functions of saturations, the model yields regions in the saturation space where the system of equations is locally elliptic. We regard elliptic behavior as a nonphysical artifact of an incomplete formulation, and derive conditions on the relative permeabilities that ensure strict hyperbolicity of the governing equations. The key point is to acknowledge that a Darcy-type formulation is insufficient to capture all the physics of three-phase flow and that, consequently, the relative permeabilities are functionals that depend on the fluid viscosity ratio and the gravity number. The derived conditions are consistent with the type of displacements that take place in porous media. By means of an illustrative example, we show how elliptic behavior can be removed, even when using simplistic relative permeability models.

  1. Composite gravitational-wave detection of compact binary coalescence

    SciTech Connect

    Cannon, Kipp; Hanna, Chad; Keppel, Drew; Searle, Antony C.

    2011-04-15

    The detection of gravitational waves from compact binaries relies on a computationally burdensome processing of gravitational-wave detector data. The parameter space of compact-binary-coalescence gravitational waves is large and optimal detection strategies often require nearly redundant calculations. Previously, it has been shown that singular value decomposition of search filters removes redundancy. Here we will demonstrate the use of singular value decomposition for a composite detection statistic. This can greatly improve the prospects for a computationally feasible rapid detection scheme across a large compact binary parameter space.

  2. Spectral/HP Element Method With Hierarchical Reconstruction for Solving Hyperbolic Conservation Laws

    SciTech Connect

    Xu, Zhiliang; Lin, Guang

    2009-12-01

    Hierarchical reconstruction (HR) has been successfully applied to prevent oscillations in solutions computed by finite volume, discontinuous Galerkin, spectral volume schemes when solving hyperbolic conservation laws. In this paper, we demonstrate that HR can also be combined with spectral/hp element methods for solving hyperbolic conservation laws. We show that HR preserves the order of accuracy of spectral/hp element methods for smooth solutions and generate essentially non-oscillatory solution profiles for shock wave problems.

  3. Does hyperbolicity impede emergence of chimera states in networks of nonlocally coupled chaotic oscillators?

    NASA Astrophysics Data System (ADS)

    Semenova, N.; Zakharova, A.; Schöll, E.; Anishchenko, V.

    2015-11-01

    We analyze nonlocally coupled networks of identical chaotic oscillators with either time-discrete or time-continuous dynamics (Henon map, Lozi map, Lorenz system). We hypothesize that chimera states, in which spatial domains of coherent (synchronous) and incoherent (desynchronized) dynamics coexist, can be obtained only in networks of oscillators with nonhyperbolic chaotic attractors and cannot be found in networks of systems with hyperbolic chaotic attractors. This hypothesis is supported by analytical results and numerical simulations for hyperbolic and nonhyperbolic cases.

  4. On the numerical solution of hyperbolic equations with singular source terms

    NASA Astrophysics Data System (ADS)

    Turk, Irfan; Ashyraliyev, Maksat

    2014-08-01

    A numerical study for hyperbolic equations having singular source terms is presented. Singular in the sense that within the spatial domain the source is defined by a Dirac delta function. Solutions of such problems will have discontinuities which forms an obstacle for standard numerical methods. In this paper, a fifth order flux implicit WENO method with non-uniform meshes is studied for approximate solutions of hyperbolic equations having singular source terms. Numerical examples are provided.

  5. Numerical test for hyperbolicity of chaotic dynamics in time-delay systems.

    PubMed

    Kuptsov, Pavel V; Kuznetsov, Sergey P

    2016-07-01

    We develop a numerical test of hyperbolicity of chaotic dynamics in time-delay systems. The test is based on the angle criterion and includes computation of angle distributions between expanding, contracting, and neutral manifolds of trajectories on the attractor. Three examples are tested. For two of them, previously predicted hyperbolicity is confirmed. The third one provides an example of a time-delay system with nonhyperbolic chaos. PMID:27575062

  6. Asymptotic stability of rarefaction waves for 2 ∗ 2 viscous hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Xin, Zhouping

    This paper concerns the asymptotic behavior toward rarefaction waves of the solution of a general 2 × 2 hyperbolic conservation laws with positive viscosity. We prove that if the initial data is close to a constant state and its values at ±∞ lie on the kth rarefaction curve for the corresponding hyperbolic conservation laws, then the solution tends as t → ∞ to the rarefaction wave determined by these states.

  7. Finite difference numerical methods for boundary control problems governed by hyperbolic partial differential equations

    NASA Technical Reports Server (NTRS)

    Chen, G.; Zheng, Q.; Coleman, M.; Weerakoon, S.

    1983-01-01

    This paper briefly reviews convergent finite difference schemes for hyperbolic initial boundary value problems and their applications to boundary control systems of hyperbolic type which arise in the modelling of vibrations. These difference schemes are combined with the primal and the dual approaches to compute the optimal control in the unconstrained case, as well as the case when the control is subject to inequality constraints. Some of the preliminary numerical results are also presented.

  8. Numerical test for hyperbolicity of chaotic dynamics in time-delay systems

    NASA Astrophysics Data System (ADS)

    Kuptsov, Pavel V.; Kuznetsov, Sergey P.

    2016-07-01

    We develop a numerical test of hyperbolicity of chaotic dynamics in time-delay systems. The test is based on the angle criterion and includes computation of angle distributions between expanding, contracting, and neutral manifolds of trajectories on the attractor. Three examples are tested. For two of them, previously predicted hyperbolicity is confirmed. The third one provides an example of a time-delay system with nonhyperbolic chaos.

  9. The entropy rate admissibility criterion for solution of hyperbolic conservation laws

    NASA Technical Reports Server (NTRS)

    Dafermos, C. M.

    1972-01-01

    The entropy rate admissibility criterion for solutions of hyperbolic conservation laws is numerically analyzed. The following admissibility criterion for solutions of hyperbolic conservation laws is proposed: a weak solution is admissible if the total entropy decays with the highest possible rate. The equivalence of this criterion and viscosity criterion is established for the single equation and the system of equations of one dimensional nonlinear elasticity.

  10. GRAVITATIONALLY FOCUSED DARK MATTER AROUND COMPACT STARS

    SciTech Connect

    Bromley, Benjamin C.

    2011-12-01

    If dark matter self-annihilates then it may produce an observable signal when its density is high. The details depend on the intrinsic properties of dark matter and how it clusters in space. For example, the density profile of some dark matter candidates may rise steeply enough toward the Galactic Center that self-annihilation may produce detectable {gamma}-ray emission. Here, we discuss the possibility that an annihilation signal arises near a compact object (e.g., neutron star or black hole) even when the density of dark matter in the neighborhood of the object is uniform. Gravitational focusing produces a local enhancement of density with a profile that falls off approximately as the inverse square-root of distance from the compact star. While geometric dilution may overwhelm the annihilation signal from this local enhancement, magnetic fields tied to the compact object can increase the signal's contrast relative to the background.

  11. Incompletely compacted equilibrated ordinary chondrites

    SciTech Connect

    Sasso, M.R.; Macke, R.J.; Boesenberg, J.S.; Britt, D.T.; Rovers, M.L.; Ebel, D.S.; Friedrich, J.M.

    2010-01-22

    We document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high-resolution synchrotron X-ray microtomography ({mu}CT) and helium pycnometry. We found total porosities ranging from {approx}10 to 20% within these chondrites, and with {mu}CT we show that up to 64% of the void space is located within intergranular voids within the rock. Given the low (S1-S2) shock stages of the samples and the large voids between mineral grains, we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history. With Fe metal and FeS metal abundances and grain size distributions, we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism. These materials were not 'fluffed' on their parent body by impact-related regolith gardening or events caused by seismic vibrations. Samples of all three chemical types of ordinary chondrites (LL, L, H) are represented in this study and we conclude that incomplete compaction is common within the asteroid belt.

  12. On a fourth order accurate implicit finite difference scheme for hyperbolic conservation laws. I - Nonstiff strongly dynamic problems

    NASA Technical Reports Server (NTRS)

    Harten, A.; Tal-Ezer, H.

    1981-01-01

    An implicit finite difference method of fourth order accuracy in space and time is introduced for the numerical solution of one-dimensional systems of hyperbolic conservation laws. The basic form of the method is a two-level scheme which is unconditionally stable and nondissipative. The scheme uses only three mesh points at level t and three mesh points at level t + delta t. The dissipative version of the basic method given is conditionally stable under the CFL (Courant-Friedrichs-Lewy) condition. This version is particularly useful for the numerical solution of problems with strong but nonstiff dynamic features, where the CFL restriction is reasonable on accuracy grounds. Numerical results are provided to illustrate properties of the proposed method.

  13. Intermittent appearances of saddle-type hyperbolic dynamics during human stick balancing on a manually controlled cart.

    PubMed

    Yoshikawa, Naoya; Suzuki, Yasuyuki; Kiyono, Ken; Nomura, Taishin

    2015-08-01

    Stabilization of an inverted pendulum on a manually controlled cart (cart-inverted pendulum; CIP), analogous to human fingertip stick balancing, is considered to get insights of how the human central nervous system stabilizes unstable dynamics. We explore a possibility that a type of intermittent control strategy proposed for human postural control might also be applicable to the CIP task, i.e., whether a transient contracting dynamics along a stable manifold of a saddle-type equilibrium of the non-controlled inverted pendulum is exploited intermittently. To this end, we measured task performances during CIP balancing from several experimental subjects. Intermittent appearances of hyperbolicity as typical characteristics reflecting the intermittent control strategy were examined in the recorded motion data using phase space analysis and wavelet analysis. We show that skilled subjects tend to exhibit those characteristics, suggesting that they stabilize upright posture of the stick by utilizing the intermittent control strategy. PMID:26737047

  14. Junction-Generalized Riemann Problem for stiff hyperbolic balance laws in networks: An implicit solver and ADER schemes

    NASA Astrophysics Data System (ADS)

    Contarino, Christian; Toro, Eleuterio F.; Montecinos, Gino I.; Borsche, Raul; Kall, Jochen

    2016-06-01

    In this paper we design a new implicit solver for the Junction-Generalized Riemann Problem (J-GRP), which is based on a recently proposed implicit method for solving the Generalized Riemann Problem (GRP) for systems of hyperbolic balance laws. We use the new J-GRP solver to construct an ADER scheme that is globally explicit, locally implicit and with no theoretical accuracy barrier, in both space and time. The resulting ADER scheme is able to deal with stiff source terms and can be applied to non-linear systems of hyperbolic balance laws in domains consisting on networks of one-dimensional sub-domains. In this paper we specifically apply the numerical techniques to networks of blood vessels. We report on a test problem with exact solution for a simplified network of three vessels meeting at a single junction, which is then used to carry out a systematic convergence rate study of the proposed high-order numerical methods. Schemes up to fifth order of accuracy in space and time are implemented and tested. We then show the ability of the ADER scheme to deal with stiff sources through a numerical simulation in a network of vessels. An application to a physical test problem consisting of a network of 37 compliant silicon tubes (arteries) and 21 junctions, reveals that it is imperative to use high-order methods at junctions, in order to preserve the desired high order of accuracy in the full computational domain. For example, it is demonstrated that a second-order method throughout, gives comparable results to a method that is fourth order in the interior of the domain and first order at junctions.

  15. A compact solid state laser

    NASA Astrophysics Data System (ADS)

    Pati, Bhabana; Park, Eric D.; Stebbins, Kenneth

    2016-03-01

    A compact laser producing green wavelength with a volume of < 8 cm3 and a weight of < 80 g finds its application in many fields from military to space based. We built a small solid-state laser that produces 1 mJ of energy per-pulse at a 1 - 20 Hz repetition rate. The laser is passively Q-switched using a Cr4+:YAG saturable absorber to generate pulses <10 ns. A nonlinear crystal doubles the frequency to generate light at 523 nm. The laser is side-pumped by a single bar diode laser using a unique pump cavity to homogenize the pump intensity in the laser rod. The laser components can easily be modified to change the output wavelength from UV to mid IR.

  16. Stable transitivity of Heisenberg group extensions of hyperbolic systems

    NASA Astrophysics Data System (ADS)

    Niţică, Viorel; Török, Andrei

    2014-04-01

    We consider skew-extensions with fibre the standard real Heisenberg group { H}_n of a uniformly hyperbolic dynamical system. We show that among the Cr extensions (r > 0) that avoid an obvious obstruction, those that are topologically transitive contain an open and dense set. More precisely, we show that an { H}_n -extension is transitive if and only if the { R}^{2n} -extension given by the Abelianization of { H}_n is transitive. A new technical tool introduced in the paper, which is of independent interest, is a diophantine approximation result. We show, under general conditions, the existence of an infinite set of approximate positive integer solutions for a diophantine system of equations consisting of a quadratic indefinite form and several linear equations. The set of approximate solutions can be chosen to point in a certain direction. The direction can be chosen from a residual subset of full measure of the set of real directions solving the system of equations exactly. Another contribution of the paper, which is used in the proof of the main result, but it is also of independent interest, is the solution of the so-called semigroup problem for the Heisenberg group. We show that for a subset S\\subset { H}_n , which avoids any maximal semigroup with non-empty interior, the closure of the semigroup generated by S is actually a group.

  17. Gain-enhanced hyperbolic metamaterials at telecommunication frequencies (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Smalley, Joseph S. T.; Vallini, Felipe; Kante, Boubacar; Shahin, Shiva; Riley, Conor; Fainman, Yeshaiahu

    2015-09-01

    Using effective medium theory (EMT), Bloch's theorem (BT), and the transfer matrix method (TMM), we analyze the possibility of gain-enhanced transmission in metamaterials with hyperbolic dispersion at telecommunication frequencies. We compare different combinations of dissipative metals and active dielectrics, including noble metals, transparent conducting oxides (TCO), III-V compounds, and solid-state dopants. We find that both indium gallium arsenide phosphide (InGaAsP) and erbium-doped silica (Er:SiO2), when combined with silver, show promise as a platform for demonstration of pump-dependent transmission. On the other hand, when these active dielectrics are combined with aluminum-doped zinc oxide (AZO), a low-loss TCO, gain-enhanced transmission is negligible. Results based on EMT are compared to the more accurate BT and TMM. When losses are ignored, quantitative agreement between these analytical techniques is observed near the center of the first Brillouin zone of a one-dimensional periodic structure. Including realistic levels of loss and gain, however, EMT predictions become overly optimistic compared to BT and TMM. We also discuss the limitations to assumptions inherent to EMT, BT, and TMM, and suggest avenues for future analysis.

  18. Extreme sensitivity biosensing platform based on hyperbolic metamaterials

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; Alapan, Yunus; ElKabbash, Mohamed; Ilker, Efe; Hinczewski, Michael; Gurkan, Umut A.; De Luca, Antonio; Strangi, Giuseppe

    2016-01-01

    Optical sensor technology offers significant opportunities in the field of medical research and clinical diagnostics, particularly for the detection of small numbers of molecules in highly diluted solutions. Several methods have been developed for this purpose, including label-free plasmonic biosensors based on metamaterials. However, the detection of lower-molecular-weight (<500 Da) biomolecules in highly diluted solutions is still a challenging issue owing to their lower polarizability. In this context, we have developed a miniaturized plasmonic biosensor platform based on a hyperbolic metamaterial that can support highly confined bulk plasmon guided modes over a broad wavelength range from visible to near infrared. By exciting these modes using a grating-coupling technique, we achieved different extreme sensitivity modes with a maximum of 30,000 nm per refractive index unit (RIU) and a record figure of merit (FOM) of 590. We report the ability of the metamaterial platform to detect ultralow-molecular-weight (244 Da) biomolecules at picomolar concentrations using a standard affinity model streptavidin–biotin. PMID:27019384

  19. Extreme sensitivity biosensing platform based on hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Sreekanth, Kandammathe Valiyaveedu; Alapan, Yunus; Elkabbash, Mohamed; Ilker, Efe; Hinczewski, Michael; Gurkan, Umut A.; de Luca, Antonio; Strangi, Giuseppe

    2016-06-01

    Optical sensor technology offers significant opportunities in the field of medical research and clinical diagnostics, particularly for the detection of small numbers of molecules in highly diluted solutions. Several methods have been developed for this purpose, including label-free plasmonic biosensors based on metamaterials. However, the detection of lower-molecular-weight (<500 Da) biomolecules in highly diluted solutions is still a challenging issue owing to their lower polarizability. In this context, we have developed a miniaturized plasmonic biosensor platform based on a hyperbolic metamaterial that can support highly confined bulk plasmon guided modes over a broad wavelength range from visible to near infrared. By exciting these modes using a grating-coupling technique, we achieved different extreme sensitivity modes with a maximum of 30,000 nm per refractive index unit (RIU) and a record figure of merit (FOM) of 590. We report the ability of the metamaterial platform to detect ultralow-molecular-weight (244 Da) biomolecules at picomolar concentrations using a standard affinity model streptavidin-biotin.

  20. Generalized harmonic spatial coordinates and hyperbolic shift conditions

    SciTech Connect

    Alcubierre, Miguel; Corichi, Alejandro; Nunez, Dario; Salgado, Marcelo; Gonzalez, Jose A.; Reimann, Bernd

    2005-12-15

    We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona et al., and closely related to dynamic shift conditions recently proposed by Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic spatial coordinates imply a condition for the shift vector that has the form of an evolution equation for the shift components. We find that in order to decouple the slicing condition from the evolution equation for the shift it is necessary to use a rescaled shift vector. The initial form of the generalized harmonic shift condition is not spatially covariant, but we propose a simple way to make it fully covariant so that it can be used in coordinate systems other than Cartesian. We also analyze the effect of the shift condition proposed here on the hyperbolicity of the evolution equations of general relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible development of blowups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition.

  1. Extreme sensitivity biosensing platform based on hyperbolic metamaterials.

    PubMed

    Sreekanth, Kandammathe Valiyaveedu; Alapan, Yunus; ElKabbash, Mohamed; Ilker, Efe; Hinczewski, Michael; Gurkan, Umut A; De Luca, Antonio; Strangi, Giuseppe

    2016-06-01

    Optical sensor technology offers significant opportunities in the field of medical research and clinical diagnostics, particularly for the detection of small numbers of molecules in highly diluted solutions. Several methods have been developed for this purpose, including label-free plasmonic biosensors based on metamaterials. However, the detection of lower-molecular-weight (<500 Da) biomolecules in highly diluted solutions is still a challenging issue owing to their lower polarizability. In this context, we have developed a miniaturized plasmonic biosensor platform based on a hyperbolic metamaterial that can support highly confined bulk plasmon guided modes over a broad wavelength range from visible to near infrared. By exciting these modes using a grating-coupling technique, we achieved different extreme sensitivity modes with a maximum of 30,000 nm per refractive index unit (RIU) and a record figure of merit (FOM) of 590. We report the ability of the metamaterial platform to detect ultralow-molecular-weight (244 Da) biomolecules at picomolar concentrations using a standard affinity model streptavidin-biotin. PMID:27019384

  2. Highly accurate adaptive finite element schemes for nonlinear hyperbolic problems

    NASA Astrophysics Data System (ADS)

    Oden, J. T.

    1992-08-01

    This document is a final report of research activities supported under General Contract DAAL03-89-K-0120 between the Army Research Office and the University of Texas at Austin from July 1, 1989 through June 30, 1992. The project supported several Ph.D. students over the contract period, two of which are scheduled to complete dissertations during the 1992-93 academic year. Research results produced during the course of this effort led to 6 journal articles, 5 research reports, 4 conference papers and presentations, 1 book chapter, and two dissertations (nearing completion). It is felt that several significant advances were made during the course of this project that should have an impact on the field of numerical analysis of wave phenomena. These include the development of high-order, adaptive, hp-finite element methods for elastodynamic calculations and high-order schemes for linear and nonlinear hyperbolic systems. Also, a theory of multi-stage Taylor-Galerkin schemes was developed and implemented in the analysis of several wave propagation problems, and was configured within a general hp-adaptive strategy for these types of problems. Further details on research results and on areas requiring additional study are given in the Appendix.

  3. Hyperbolic asymptotics in Burgers' turbulence and extremal processes

    NASA Astrophysics Data System (ADS)

    Molchanov, S. A.; Surgailis, D.; Woyczynski, W. A.

    1995-03-01

    Large time asymptotics of statistical solution u(t,x) (1.2) of the Burgers' equation (1.1) is considered, where ξ(x)=ξ L(x) is a stationary zero mean Gaussian process depending on a large parameter L>0 so that 220_2005_Article_BF02099589_TeX2GIFE1.gif ξ _L (x) ˜ σ _L η (x/L)(L to infty ), whereσ _L = L^2 (2log L)^{1/2} and η( x) is a given standardized stationary Gaussian process. We prove that as L→∞ the hyperbolicly scaled random fields u(L 2t, L2x) converge in distribution to a random field with “saw-tooth” trajectories, defined by means of a Poisson process on the plane related to high fluctuations of ξ( x), which corresponds to the zero viscosity solutions. At the physical level of rigor, such asymptotics was considered before by Gurbatov, Malakhov and Saichev (1991).

  4. An elliptic hyperbolic free boundary problem modelling cancer therapy

    NASA Astrophysics Data System (ADS)

    Tao, Youshan; Chen, Miaojun

    2006-02-01

    In this paper we study a free boundary problem modelling the growth of an avascular tumour with drug application. The tumour consists of two cell populations: live cells and dead cells. The densities of these cells satisfy a system of nonlinear first order hyperbolic equations. The tumour surface is a moving boundary, which satisfies an integro-differential equation. The nutrient concentration and the drug concentration satisfy nonlinear diffusion equations. The nutrient drives the growth of the tumour, whereas the drug is capable of killing cells with Michaelis-Menten kinetics. We prove that this free boundary problem has a unique global solution. Furthermore, we investigate the combined effects of a drug and a nutrient on an avascular tumour growth. We prove that the tumour shrinks to a necrotic core with radius Rs > 0 and that the global solution converges to a trivial steady-state solution under some natural assumptions on the model parameters. We also prove that an untreated tumour shrinks to a dead core or continually grows to an infinite size, which depends on the different parameter conditions.

  5. One-way spatial integration of hyperbolic equations

    NASA Astrophysics Data System (ADS)

    Towne, Aaron; Colonius, Tim

    2015-11-01

    In this paper, we develop and demonstrate a method for constructing well-posed one-way approximations of linear hyperbolic systems. We use a semi-discrete approach that allows the method to be applied to a wider class of problems than existing methods based on analytical factorization of idealized dispersion relations. After establishing the existence of an exact one-way equation for systems whose coefficients do not vary along the axis of integration, efficient approximations of the one-way operator are constructed by generalizing techniques previously used to create nonreflecting boundary conditions. When physically justified, the method can be applied to systems with slowly varying coefficients in the direction of integration. To demonstrate the accuracy and computational efficiency of the approach, the method is applied to model problems in acoustics and fluid dynamics via the linearized Euler equations; in particular we consider the scattering of sound waves from a vortex and the evolution of hydrodynamic wavepackets in a spatially evolving jet. The latter problem shows the potential of the method to offer a systematic, convergent alternative to ad hoc regularizations such as the parabolized stability equations.

  6. Limestone compaction: an enigma

    USGS Publications Warehouse

    Shinn, Eugene A.; Halley, Robert B.; Hudson, J. Harold; Lidz, Barbara H.

    1977-01-01

    Compression of an undisturbed carbonate sediment core under a pressure of 556 kg/cm2 produced a “rock” with sedimentary structures similar to typical ancient fine-grained limestones. Surprisingly, shells, foraminifera, and other fossils were not noticeably crushed, which indicates that absence of crushed fossils in ancient limestones can no longer be considered evidence that limestones do not compact.

  7. Compact optical transconductance varistor

    SciTech Connect

    Sampayan, Stephen

    2015-09-22

    A compact radiation-modulated transconductance varistor device having both a radiation source and a photoconductive wide bandgap semiconductor material (PWBSM) integrally formed on a substrate so that a single interface is formed between the radiation source and PWBSM for transmitting PWBSM activation radiation directly from the radiation source to the PWBSM.

  8. Composite Space Telescope Truss

    NASA Video Gallery

    NASA engineers are recycling an idea for a lightweight, compact space telescope structure from the early 1990s. The 315 struts and 84 nodes were originally designed to enable spacewalking astronaut...

  9. Progress in Compact Toroid Experiments

    SciTech Connect

    Dolan, Thomas James

    2002-09-01

    The term "compact toroids" as used here means spherical tokamaks, spheromaks, and field reversed configurations, but not reversed field pinches. There are about 17 compact toroid experiments under construction or operating, with approximate parameters listed in Table 1.

  10. The dynamics of compact laser pulses

    NASA Astrophysics Data System (ADS)

    Goto, S.; Tucker, R. W.; Walton, T. J.

    2016-07-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium in terms of an effective quantum Hamiltonian.

  11. Two-mirror, three-reflection telescopes as candidates for sky surveys in ground and space applications. The MINITRUST: an active optics warping telescope for wide-field astronomy

    NASA Astrophysics Data System (ADS)

    Viotti, Roberto F.; La Padula, Cesare D.; Vignato, Agostino; Lemaitre, Gerard R.; Montiel, Pierre; Dohlen, Kjetil

    2002-12-01

    A concept based on a two-mirror, three-reflection telescope has been investigated. Its anastigmatism and flat fielded properties, the compactness and optical performances over 2-2.5 arc deg field of view, make this optical system of high interest for the development of much larger telescopes than with Schmidt designs. The 2MTRT concept is a potential candidate for sky surveys with 2-3 meter class telescopes and particularily well adapted for UV space surveys. Preliminary developments have been carried out with the construction of a 30-cm prototype on Amoretti's design, providing encouraging results. At present, a 45-cm 2MTRT prototype has been realized for ground based sky survey of NEOs, based on active optics (MINITRUST), in order to overcome the difficulty of obtaining three aspherical surfaces. The primary and tertiary lie on the same double vase substrate, and have a rest profile. The hyperbolization is carried out in situ by air depressure. The secondary, in a tulip form substrate, has been hyperbolized by elastic relaxation. The project is planned for operation in 2003.

  12. Parallel hyperbolic PDE simulation on clusters: Cell versus GPU

    NASA Astrophysics Data System (ADS)

    Rostrup, Scott; De Sterck, Hans

    2010-12-01

    Increasingly, high-performance computing is looking towards data-parallel computational devices to enhance computational performance. Two technologies that have received significant attention are IBM's Cell Processor and NVIDIA's CUDA programming model for graphics processing unit (GPU) computing. In this paper we investigate the acceleration of parallel hyperbolic partial differential equation simulation on structured grids with explicit time integration on clusters with Cell and GPU backends. The message passing interface (MPI) is used for communication between nodes at the coarsest level of parallelism. Optimizations of the simulation code at the several finer levels of parallelism that the data-parallel devices provide are described in terms of data layout, data flow and data-parallel instructions. Optimized Cell and GPU performance are compared with reference code performance on a single x86 central processing unit (CPU) core in single and double precision. We further compare the CPU, Cell and GPU platforms on a chip-to-chip basis, and compare performance on single cluster nodes with two CPUs, two Cell processors or two GPUs in a shared memory configuration (without MPI). We finally compare performance on clusters with 32 CPUs, 32 Cell processors, and 32 GPUs using MPI. Our GPU cluster results use NVIDIA Tesla GPUs with GT200 architecture, but some preliminary results on recently introduced NVIDIA GPUs with the next-generation Fermi architecture are also included. This paper provides computational scientists and engineers who are considering porting their codes to accelerator environments with insight into how structured grid based explicit algorithms can be optimized for clusters with Cell and GPU accelerators. It also provides insight into the speed-up that may be gained on current and future accelerator architectures for this class of applications. Program summaryProgram title: SWsolver Catalogue identifier: AEGY_v1_0 Program summary URL

  13. Trading spaces: building three-dimensional nets from two-dimensional tilings

    PubMed Central

    Castle, Toen; Evans, Myfanwy E.; Hyde, Stephen T.; Ramsden, Stuart; Robins, Vanessa

    2012-01-01

    We construct some examples of finite and infinite crystalline three-dimensional nets derived from symmetric reticulations of homogeneous two-dimensional spaces: elliptic (S2), Euclidean (E2) and hyperbolic (H2) space. Those reticulations are edges and vertices of simple spherical, planar and hyperbolic tilings. We show that various projections of the simplest symmetric tilings of those spaces into three-dimensional Euclidean space lead to topologically and geometrically complex patterns, including multiple interwoven nets and tangled nets that are otherwise difficult to generate ab initio in three dimensions. PMID:24098839

  14. Compact Radio Sources in NGC 660

    NASA Astrophysics Data System (ADS)

    Wiercigroch, A. B.

    1995-12-01

    The nuclei of starburst galaxies are often obscured by dust and hence are probed best in non-visual wavelength regimes such as the infrared and radio. For example, radio studies of classical starburst galaxies such as NGC 253 and M82 have identified ~ 50 compact sources in each galaxy. One of the purposes of this type of observing program has been to classify the compact radio sources as H II regions or radio supernovae, and to estimate the supernova rates. If obtainable, spectral indices are used to identify the compact structures; otherwise supporting evidence or assumptions are needed. NGC 660, located at a distance of 7.5 Mpc, is a strong candidate for a search for compact radio sources. It is a relatively strong infrared emitter, has far infrared colors similar to NGC 253 and M82, and shows several peaks in published Very Large Array (VLA) maps at 6 cm and 20 cm. We therefore observed NGC 660 at 3.6 cm in the A-configuration of the VLA on 1995 July 13--14. Total integration time on-source was 4.8 hrs. The image shows a large family ( ~ 20) of compact radio structures with a flux density range of 0.1--3.4 mJy, three of which have fluxes > 2.0 mJy. The source luminosities are comparable to those of the stronger sources in M82 and NGC 253, typically a few times more powerful than Cas A. A number of the compact sources appear to lie along a ring projected against the more diffuse radio emission in the galaxy's nuclear region. The work described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  15. Observational properties of compact groups of galaxies

    NASA Technical Reports Server (NTRS)

    Hickson, Paul

    1990-01-01

    Compact groups are small, relatively isolated, systems of galaxies with projected separations comparable to the diameters of the galaxies themselves. Two well-known examples are Stephan's Quintet (Stephan, 1877) and Seyfert's Sextet (Seyfert 1948a,b). In groups such as these, the apparent space density of galaxies approaches 10(exp 6) Mpc(sub -3), denser even than the cores of rich clusters. The apparent unlikeliness of the chance occurrence of such tight groupings lead Ambartsumyan (1958, 1975) to conclude that compact groups must be physically dense systems. This view is supported by clear signs of galaxy interactions that are seen in many groups. Spectroscopic observations reveal that typical relative velocities of galaxies in the groups are comparable to their internal stellar velocities. This should be conducive to strong gravitational interactions - more so than in rich clusters, where galaxy velocities are typically much higher. This suggests that compact groups could be excellent laboratories in which to study galaxy interactions and their effects. Compact groups often contain one or more galaxies whose redshift differs greatly from those of the other group members. If these galaxies are at the same distance as the other members, either entire galaxies are being ejected at high velocities from these groups, or some new physical phenomena must be occurring. If their redshifts are cosmological, we must explain why so many discordant galaxies are found in compact groups. In recent years much progress has been made in addressing these questions. Here, the author discusses the current observational data on compact groups and their implications.

  16. Hyperbolic meteors: Interstellar or generated locally via the gravitational slingshot effect?

    NASA Astrophysics Data System (ADS)

    Wiegert, Paul A.

    2014-11-01

    The arrival of solid particles from outside our Solar System would present us with an invaluable source of scientific information. Attempts to detect such interstellar particles among the meteors observed in Earth's atmosphere have almost exclusively assumed that those particles moving above the Solar System's escape speed - particles on orbits hyperbolic with respect to the Sun - were precisely the extrasolar particles being searched for. Here we show that hyperbolic particles can be generated entirely within the Solar System by gravitational scattering of interplanetary dust and meteoroids by the planets. These particles have necessarily short lifetimes as they quickly escape our star system; nonetheless some may arrive at Earth at speeds comparable to those expected of interstellar meteoroids. Some of these are associated with the encounter of planets with the debris streams of individual comets: Comet C/1995 O1 Hale-Bopp's 1996 pre-perihelion encounter with Jupiter could have scattered particles that would have reached our planet with velocities of almost 1 km s-1 above the hyperbolic velocity at Earth; however, such encounters are relatively rare. The rates of occurrence of hyperbolically-scattered sporadic meteors are also quite low. Only one of every ∼104 optical meteors observed at Earth is expected to be such a locally generated hyperbolic and its heliocentric velocity is typically only a hundred metres per second above the heliocentric escape velocity at Earth's orbit. The majority of such gravitationally-scattered hyperbolics originate at Mercury, though Venus and Mars also contribute. Mercury and Venus are predicted to generate weak 'hyperbolic meteor showers': the restrictive geometry of scattering to our planet means that a radiant near the Sun from which hyperbolic meteors arrive at Earth should recur with the planet's synodic period. However, though planetary scattering can produce meteoroids with speeds comparable to interstellar meteors and at

  17. Marginally trapped submanifolds in Lorentzian space forms and in the Lorentzian product of a space form by the real line

    SciTech Connect

    Anciaux, Henri; Godoy, Yamile

    2015-02-15

    We give local, explicit representation formulas for n-dimensional spacelike submanifolds which are marginally trapped in the Minkowski space ℝ{sub 1}{sup n+2}, the de Sitter space dS{sup n+2}, the anti-de Sitter space AdS{sup n+2} and the Lorentzian products S{sup n+1} × ℝ and ℍ{sup n+1} × ℝ of the sphere and the hyperbolic space by the real line.

  18. Compact power reactor

    DOEpatents

    Wetch, Joseph R.; Dieckamp, Herman M.; Wilson, Lewis A.

    1978-01-01

    There is disclosed a small compact nuclear reactor operating in the epithermal neutron energy range for supplying power at remote locations, as for a satellite. The core contains fuel moderator elements of Zr hydride with 7 w/o of 93% enriched uranium alloy. The core has a radial beryllium reflector and is cooled by liquid metal coolant such as NaK. The reactor is controlled and shut down by moving portions of the reflector.

  19. Compact heat exchangers

    SciTech Connect

    Kays, W.M.; London, A.L.

    1984-01-01

    This third edition is an update of the second edition published in 1964. New data and more modern theoretical solutions for flow in the simple geometries are included, although this edition does not differ radically from the second edition. It contains basic test data for eleven new surface configurations, including some of the very compact ceramic matrices. Al dimensions are given in both the English and the Systeme International (SI) system of units.

  20. Compact infrared detector

    NASA Technical Reports Server (NTRS)

    Gupta, A.; Hong, S.; Moacanin, J.

    1981-01-01

    Broadband IR detector integrated into compact package for pollution monitoring and weather prediction is small, highly responsive, and immune to high noise. Sensing material is transparent sheet metalized with reflecting coating and overcoated with black material on same side. Pulse produced by chopping of infrared source beam creates transient "thermal lens" that temporarily defocuses laser beam probe. Detector monitoring beam measures defocusing which parallels infrared intensity.

  1. Granule consolidation during compaction.

    PubMed

    Rubinstein, M H

    1976-03-01

    The deformation of small cylindrical aggregates of dibasic calcium phosphate was measured during compaction. An analogy between these aggregates and cylindrical granules was proposed. No change in the original shape of the aggregates occurred; the cylindrical shape was maintained even at high compaction pressures. Relaxation of the aggregates occurred at pressures higher than 420 MNm-2 (60.9 x 10(3) lb in.-2) when removed from the compacts, but no relaxation took place at pressures below this value. In addition, the aggregates relaxed by an increase in thickness only; there was no corresponding change in diameter. Up to a pressure of 200 MNm-2 (29.0 x 10(3) lb in.-2), an increase in aggregate diameter occurred, which was accompanied by a reduction in thickness. This change produced only a small reduction in volume, which was attributable to interparticulate slippage resulting in a closer packed arrangement. At a pressure of 200 MNm-2, the aggregate diameter no longer increased because solid bridges were formed between the particles and the die wall, preventing further spreading. From 200 to 420 MNm-2, failure of the material occurred by plastic deformation, which produced only a decrease in aggregate thickness. From 420 to 800 MNm-2 (116.0 x 10(3) lb in.-2), a structure was formed that could support the applied load without further reduction of thickness, and this structure was shown to behave elastically. PMID:1263085

  2. A Novel Hyperbolization Procedure for The Two-Phase Six-Equation Flow Model

    SciTech Connect

    Samet Y. Kadioglu; Robert Nourgaliev; Nam Dinh

    2011-10-01

    We introduce a novel approach for the hyperbolization of the well-known two-phase six equation flow model. The six-equation model has been frequently used in many two-phase flow applications such as bubbly fluid flows in nuclear reactors. One major drawback of this model is that it can be arbitrarily non-hyperbolic resulting in difficulties such as numerical instability issues. Non-hyperbolic behavior can be associated with complex eigenvalues that correspond to characteristic matrix of the system. Complex eigenvalues are often due to certain flow parameter choices such as the definition of inter-facial pressure terms. In our method, we prevent the characteristic matrix receiving complex eigenvalues by fine tuning the inter-facial pressure terms with an iterative procedure. In this way, the characteristic matrix possesses all real eigenvalues meaning that the characteristic wave speeds are all real therefore the overall two-phase flowmodel becomes hyperbolic. The main advantage of this is that one can apply less diffusive highly accurate high resolution numerical schemes that often rely on explicit calculations of real eigenvalues. We note that existing non-hyperbolic models are discretized mainly based on low order highly dissipative numerical techniques in order to avoid stability issues.

  3. Proposal to produce large compact toroids

    SciTech Connect

    Phillips, J.A.

    1981-03-01

    Relatively large, hot compact toroids might be produced in the annular space between two concentric one-turn coils. With currents in the two coils flowing in the same direction, the magnetic fields on each side of the plasma are in opposite directions. As the fields are raised, the plasma ring is heated and compressed radially towards the center of the annular space. By the addition of two sets of auxiliary coils, the plasma ring can be ejected out one end of the two-coil system into a long axial magnetic field.

  4. Quantitative Compactness Estimates for Hamilton-Jacobi Equations

    NASA Astrophysics Data System (ADS)

    Ancona, Fabio; Cannarsa, Piermarco; Nguyen, Khai T.

    2016-02-01

    We study quantitative compactness estimates in {W^{1,1}_{loc}} for the map {S_t}, {t > 0} that is associated with the given initial data {u_0in Lip (R^N)} for the corresponding solution {S_t u_0} of a Hamilton-Jacobi equation u_t+Hbig(nabla_{x} ubig)=0, qquad t≥ 0,quad xinR^N, with a uniformly convex Hamiltonian {H=H(p)}. We provide upper and lower estimates of order {1/\\varepsilon^N} on the Kolmogorov {\\varepsilon}-entropy in {W^{1,1}} of the image through the map S t of sets of bounded, compactly supported initial data. Estimates of this type are inspired by a question posed by Lax (Course on Hyperbolic Systems of Conservation Laws. XXVII Scuola Estiva di Fisica Matematica, Ravello, 2002) within the context of conservation laws, and could provide a measure of the order of "resolution" of a numerical method implemented for this equation.

  5. A HLL-Rankine-Hugoniot Riemann solver for complex non-linear hyperbolic problems

    NASA Astrophysics Data System (ADS)

    Guy, Capdeville

    2013-10-01

    We present a new HLL-type approximate Riemann solver that aims at capturing any isolated discontinuity without necessitating extensive characteristic analysis of governing partial differential equations. This property is especially attractive for complex hyperbolic systems with more than two equations. Following Linde's (2002) approach [6], we introduce a generic middle wave into the classical two-state HLL solver. The property of this third wave is typified by the way of a "strength indicator" that is derived from polynomial considerations. The polynomial that constitutes the basis of the procedure is made non-oscillatory by an adapted fourth-order WENO algorithm (CWENO4). This algorithm makes it possible to derive an expression for the strength indicator. According to the size of this latter parameter, the resulting solver (HLL-RH), either computes the multi-dimensional Rankine-Hugoniot equations if an isolated discontinuity appears in the Riemann fan, or asymptotically tends towards the two-state HLL solver if the solution is locally smooth. The asymptotic version of the HLL-RH solver is demonstrated to be positively conservative and entropy satisfying in its first-order multi-dimensional form provided that a relevant and not too restrictive CFL condition is considered; specific limitations of the conservative increments of the numerical solution and a suited entropy condition enable to maintain these properties in its high-order version. With a monotonicity-preserving algorithm for the time integration, the numerical method so generated, is third order in time and fourth-order accurate in space for the smooth part of the solution; moreover, the scheme is stable and accurate when capturing a shock wave, whatever the complexity of the underlying differential system. Extensive numerical tests for the one- and two-dimensional Euler equation of gas dynamics and comparisons with classical Godunov-type methods help to point out the potentialities and insufficiencies

  6. On spectral synthesis on element-wise compact Abelian groups

    NASA Astrophysics Data System (ADS)

    Platonov, S. S.

    2015-08-01

    Let G be an arbitrary locally compact Abelian group and let C(G) be the space of all continuous complex-valued functions on G. A closed linear subspace \\mathscr H\\subseteq C(G) is referred to as an invariant subspace if it is invariant with respect to the shifts τ_y\\colon f(x)\\mapsto f(xy), y\\in G. By definition, an invariant subspace \\mathscr H\\subseteq C(G) admits strict spectral synthesis if \\mathscr H coincides with the closure in C(G) of the linear span of all characters of G belonging to \\mathscr H. We say that strict spectral synthesis holds in the space C(G) on G if every invariant subspace \\mathscr H\\subseteq C(G) admits strict spectral synthesis. An element x of a topological group G is said to be compact if x is contained in some compact subgroup of G. A group G is said to be element-wise compact if all elements of G are compact. The main result of the paper is the proof of the fact that strict spectral synthesis holds in C(G) for a locally compact Abelian group G if and only if G is element-wise compact. Bibliography: 14 titles.

  7. Negative Refraction and Energy Funneling by Hyperbolic Materials: An Experimental Demonstration in Acoustics

    NASA Astrophysics Data System (ADS)

    García-Chocano, Victor M.; Christensen, Johan; Sánchez-Dehesa, José

    2014-04-01

    This Letter reports the design, fabrication, and experimental characterization of hyperbolic materials showing negative refraction and energy funneling of airborne sound. Negative refraction is demonstrated using a stack of five holey Plexiglas plates where their thicknesses, layer separation, hole diameters, and lattice periodicity have been determined to show hyperbolic dispersion around 40 kHz. The resulting hyperbolic material shows a flat band profile in the equifrequency contour allowing the gathering of acoustic energy in a broad range of incident angles and its funneling through the material. Our demonstrations foresee interesting developments based on both phenomena. Acoustic imaging with subwavelength resolution and spot-size converters that harvest and squeeze sound waves irradiating from many directions into a collimated beam are just two possible applications among many.

  8. Hyperbolic Prismatic Grid Generation and Solution of Euler Equations on Prismatic Grids

    NASA Technical Reports Server (NTRS)

    Pandya, S. A.; Chattot, JJ; Hafez, M. M.; Kutler, Paul (Technical Monitor)

    1994-01-01

    A hyperbolic grid generation method is used to generate prismatic grids and an approach using prismatic grids to solve the Euler equations is presented. The theory of the stability and feasibility of the hyperbolic grid generation method is presented. The hyperbolic grid generation method of Steger et al for structured grids is applied to a three dimensional triangularized surface definition to generate a grid that is unstructured on each successive layer. The grid, however, retains structure in the body-normal direction and has a computational cell shaped like a triangular prism. In order to take advantage of the structure in the normal direction, a finite-volume scheme that treats the unknowns along the normal direction implicitly is introduced and the flow over a sphere is simulated.

  9. Subdiffractional focusing and guiding of polaritonic rays in a natural hyperbolic material

    NASA Astrophysics Data System (ADS)

    Dai, S.; Ma, Q.; Andersen, T.; McLeod, A. S.; Fei, Z.; Liu, M. K.; Wagner, M.; Watanabe, K.; Taniguchi, T.; Thiemens, M.; Keilmann, F.; Jarillo-Herrero, P.; Fogler, M. M.; Basov, D. N.

    2015-04-01

    Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials, light propagation is unusual leading to novel and often non-intuitive optical phenomena. Here we report infrared nano-imaging experiments demonstrating that crystals of hexagonal boron nitride, a natural mid-infrared hyperbolic material, can act as a `hyper-focusing lens' and as a multi-mode waveguide. The lensing is manifested by subdiffractional focusing of phonon-polaritons launched by metallic disks underneath the hexagonal boron nitride crystal. The waveguiding is revealed through the modal analysis of the periodic patterns observed around such launchers and near the sample edges. Our work opens new opportunities for anisotropic layered insulators in infrared nanophotonics complementing and potentially surpassing concurrent artificial hyperbolic materials with lower losses and higher optical localization.

  10. First-Order Hyperbolic System Method for Time-Dependent Advection-Diffusion Problems

    NASA Technical Reports Server (NTRS)

    Mazaheri, Alireza; Nishikawa, Hiroaki

    2014-01-01

    A time-dependent extension of the first-order hyperbolic system method for advection-diffusion problems is introduced. Diffusive/viscous terms are written and discretized as a hyperbolic system, which recovers the original equation in the steady state. The resulting scheme offers advantages over traditional schemes: a dramatic simplification in the discretization, high-order accuracy in the solution gradients, and orders-of-magnitude convergence acceleration. The hyperbolic advection-diffusion system is discretized by the second-order upwind residual-distribution scheme in a unified manner, and the system of implicit-residual-equations is solved by Newton's method over every physical time step. The numerical results are presented for linear and nonlinear advection-diffusion problems, demonstrating solutions and gradients produced to the same order of accuracy, with rapid convergence over each physical time step, typically less than five Newton iterations.

  11. A boundary value problem for first order strictly hyperbolic systems on the plane

    NASA Astrophysics Data System (ADS)

    Soldatov, Alexander P.; Zhura, Nikolay A.

    2015-11-01

    Boundary value problems, more precisely Dirichlet's problem for a string equation, or for an equivalent system of first order equations have been first studied in the first half of last century ([1] - [9]). The interest to these problems has been big ever since, see e.g. [10, 11]. All these papers have looked into the boundary value problems in a finite domains in the plane. Strictly hyperbolic systems with more than two characteristics in infinite domains, have been studied in [12, 13]. The question of boundary value problems for a hyperbolic system of equations with more than two characteristics in finite domain on the plane, when a boundary conditions are prescribed at a whole boundary of the domain, evidently remained open. In this paper, we study this problem in a finite domain on the plane for a hyperbolic system of equations of the first order with constant coefficients and with three mutually distinct characteristics.

  12. Transient modeling/analysis of hyperbolic heat conduction problems employing mixed implicit-explicit alpha method

    NASA Technical Reports Server (NTRS)

    Tamma, Kumar K.; D'Costa, Joseph F.

    1991-01-01

    This paper describes the evaluation of mixed implicit-explicit finite element formulations for hyperbolic heat conduction problems involving non-Fourier effects. In particular, mixed implicit-explicit formulations employing the alpha method proposed by Hughes et al. (1987, 1990) are described for the numerical simulation of hyperbolic heat conduction models, which involves time-dependent relaxation effects. Existing analytical approaches for modeling/analysis of such models involve complex mathematical formulations for obtaining closed-form solutions, while in certain numerical formulations the difficulties include severe oscillatory solution behavior (which often disguises the true response) in the vicinity of the thermal disturbances, which propagate with finite velocities. In view of these factors, the alpha method is evaluated to assess the control of the amount of numerical dissipation for predicting the transient propagating thermal disturbances. Numerical test models are presented, and pertinent conclusions are drawn for the mixed-time integration simulation of hyperbolic heat conduction models involving non-Fourier effects.

  13. Numerical simulation of hyperbolic heat conduction with convection boundary conditions and pulse heating effects

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Tamma, Kumar K.; Railkar, Sudhir B.

    1989-01-01

    The paper describes the numerical simulation of hyperbolic heat conduction with convection boundary conditions. The effects of a step heat loading, a sudden pulse heat loading, and an internal heat source are considered in conjunction with convection boundary conditions. Two methods of solution are presened for predicting the transient behavior of the propagating thermal disturbances. In the first method, MacCormack's predictor-corrector method is employed for integrating the hyperbolic system of equations. Next, the transfinite element method, which employs specially tailored elements, is used for accurately representing the transient response of the propagating thermal wave fronts. The agreement between the results of various numerical test cases validate the representative behavior of the thermal wave fronts. Both methods represent hyperbolic heat conduction behavior by effectively modeling the sharp discontinuities of the propagating thermal disturbances.

  14. Indium tin oxide nanowires as hyperbolic metamaterials for near-field radiative heat transfer

    SciTech Connect

    Chang, Jui-Yung; Basu, Soumyadipta Wang, Liping

    2015-02-07

    We investigate near-field radiative heat transfer between Indium Tin Oxide (ITO) nanowire arrays which behave as type 1 and 2 hyperbolic metamaterials. Using spatial dispersion dependent effective medium theory to model the dielectric function of the nanowires, the impact of filling fraction on the heat transfer is analyzed. Depending on the filling fraction, it is possible to achieve both types of hyperbolic modes. At 150 nm vacuum gap, the heat transfer between the nanowires with 0.5 filling fraction can be 11 times higher than that between two bulk ITOs. For vacuum gaps less than 150 nm the heat transfer increases as the filling fraction decreases. Results obtained from this study will facilitate applications of ITO nanowires as hyperbolic metamaterials for energy systems.

  15. Realizing high-quality ultra-large momentum states using semiconductor hyperbolic metamaterials

    DOE PAGESBeta

    Campione, Salvatore; Liu, Sheng; Luk, Ting S.; Sinclair, Michael B.

    2015-08-05

    We employ both the effective medium approximation (EMA) and Bloch theory to compare the dispersion properties of semiconductor hyperbolic metamaterials (SHMs) at mid-infrared frequencies and metallic hyperbolic metamaterials (MHMs) at visible frequencies. This analysis reveals the conditions under which the EMA can be safely applied for both MHMs and SHMs. We find that the combination of precise nanoscale layering and the longer infrared operating wavelengths puts the SHMs well within the effective medium limit and, in contrast to MHMs, allows for the attainment of very high photon momentum states. Additionally, SHMs allow for new phenomena such as ultrafast creation ofmore » the hyperbolic manifold through optical pumping. Furthermore, we examine the possibility of achieving ultrafast topological transitions through optical pumping which can photo-dope appropriately designed quantum wells on the femtosecond time scale.« less

  16. Realizing high-quality ultralarge momentum states and ultrafast topological transitions using semiconductor hyperbolic metamaterials

    DOE PAGESBeta

    Campione, Salvatore; Liu, Sheng; Luk, Ting S.; Sinclair, Michael B.

    2015-08-05

    We employ both the effective medium approximation (EMA) and Bloch theory to compare the dispersion properties of semiconductor hyperbolic metamaterials (SHMs) at mid-infrared frequencies and metallic hyperbolic metamaterials (MHMs) at visible frequencies. This analysis reveals the conditions under which the EMA can be safely applied for both MHMs and SHMs. We find that the combination of precise nanoscale layering and the longer infrared operating wavelengths puts the SHMs well within the effective medium limit and, in contrast to MHMs, allows for the attainment of very high photon momentum states. Additionally, SHMs allow for new phenomena such as ultrafast creation ofmore » the hyperbolic manifold through optical pumping. Furthermore, we examine the possibility of achieving ultrafast topological transitions through optical pumping which can photo-dope appropriately designed quantum wells on the femtosecond time scale.« less

  17. Realizing high-quality ultralarge momentum states and ultrafast topological transitions using semiconductor hyperbolic metamaterials

    SciTech Connect

    Campione, Salvatore; Liu, Sheng; Luk, Ting S.; Sinclair, Michael B.

    2015-08-05

    We employ both the effective medium approximation (EMA) and Bloch theory to compare the dispersion properties of semiconductor hyperbolic metamaterials (SHMs) at mid-infrared frequencies and metallic hyperbolic metamaterials (MHMs) at visible frequencies. This analysis reveals the conditions under which the EMA can be safely applied for both MHMs and SHMs. We find that the combination of precise nanoscale layering and the longer infrared operating wavelengths puts the SHMs well within the effective medium limit and, in contrast to MHMs, allows for the attainment of very high photon momentum states. Additionally, SHMs allow for new phenomena such as ultrafast creation of the hyperbolic manifold through optical pumping. Furthermore, we examine the possibility of achieving ultrafast topological transitions through optical pumping which can photo-dope appropriately designed quantum wells on the femtosecond time scale.

  18. Subdiffractional focusing and guiding of polaritonic rays in a natural hyperbolic material

    PubMed Central

    Dai, S.; Ma, Q.; Andersen, T.; Mcleod, A. S.; Fei, Z.; Liu, M. K.; Wagner, M.; Watanabe, K.; Taniguchi, T.; Thiemens, M.; Keilmann, F.; Jarillo-Herrero, P.; Fogler, M. M.; Basov, D. N.

    2015-01-01

    Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials, light propagation is unusual leading to novel and often non-intuitive optical phenomena. Here we report infrared nano-imaging experiments demonstrating that crystals of hexagonal boron nitride, a natural mid-infrared hyperbolic material, can act as a ‘hyper-focusing lens' and as a multi-mode waveguide. The lensing is manifested by subdiffractional focusing of phonon–polaritons launched by metallic disks underneath the hexagonal boron nitride crystal. The waveguiding is revealed through the modal analysis of the periodic patterns observed around such launchers and near the sample edges. Our work opens new opportunities for anisotropic layered insulators in infrared nanophotonics complementing and potentially surpassing concurrent artificial hyperbolic materials with lower losses and higher optical localization. PMID:25902364

  19. Realizing high-quality ultra-large momentum states using semiconductor hyperbolic metamaterials

    SciTech Connect

    Campione, Salvatore; Liu, Sheng; Luk, Ting S.; Sinclair, Michael B.

    2015-08-05

    We employ both the effective medium approximation (EMA) and Bloch theory to compare the dispersion properties of semiconductor hyperbolic metamaterials (SHMs) at mid-infrared frequencies and metallic hyperbolic metamaterials (MHMs) at visible frequencies. This analysis reveals the conditions under which the EMA can be safely applied for both MHMs and SHMs. We find that the combination of precise nanoscale layering and the longer infrared operating wavelengths puts the SHMs well within the effective medium limit and, in contrast to MHMs, allows for the attainment of very high photon momentum states. Additionally, SHMs allow for new phenomena such as ultrafast creation of the hyperbolic manifold through optical pumping. Furthermore, we examine the possibility of achieving ultrafast topological transitions through optical pumping which can photo-dope appropriately designed quantum wells on the femtosecond time scale.

  20. Enhancements to GPR buried UXO detection using the apex-shifted hyperbolic radon tansform

    NASA Astrophysics Data System (ADS)

    Masarik, Matthew P.; Thelen, Brian T.; Xique, Ismael J.

    2016-05-01

    This paper investigates the use of the apex-shifted hyperbolic Radon transform to improve detection of buried unexploded ordinances with ground penetrating radar (GPR). The forward transform, motivated by physical signatures generated by targets, is defined and implemented. The adjoint of the transform is derived and implemented as well. The transform and its adjoint are used to filter out responses that do not exhibit the hyperbolic structure characteristic of GPR target responses. The effectiveness of filtering off clutter via this hyperbolic Radon transform filtering procedure is demonstrated qualitatively on several examples of GPR B-scan imagery from a government-provided dataset collected at an outdoor testing site. Furthermore, a quantitative assessment of the utility within a detection algorithm is given in terms of improved ROC curve performance on the same dataset.