68 research outputs found

    Communications technology satellite: United States experiments and disaster communications applications

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    Ground antennas from 0.6 to 5.0 meters in diameter were used as remote earth terminals by the United States for both wideband (television) and narrowband (voice, data) communication in conjunction with the Canadian Hermes satellite's high power transmitter. Experiments summarized cover teleconferencing and duplex videoconferencing for medical, educational, and civic purposes, as well as the remote interpretation of multilingual broadcasts from the United Nations. The capabilities of the system during real and simulated disasters at airports are assessed. Particular attention is given to miniexperiments for flood control in the Mississippi River basin and in Johnstown, Pennsylvania during the 1977 flood

    Description of the SERT 2 spacecraft and mission

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    Performance and orbital flight plan of SERT 2 ion thruster spacecraf

    The Effect of Planarization on Width

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    We study the effects of planarization (the construction of a planar diagram DD from a non-planar graph GG by replacing each crossing by a new vertex) on graph width parameters. We show that for treewidth, pathwidth, branchwidth, clique-width, and tree-depth there exists a family of nn-vertex graphs with bounded parameter value, all of whose planarizations have parameter value Ω(n)\Omega(n). However, for bandwidth, cutwidth, and carving width, every graph with bounded parameter value has a planarization of linear size whose parameter value remains bounded. The same is true for the treewidth, pathwidth, and branchwidth of graphs of bounded degree.Comment: 15 pages, 6 figures. To appear at the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

    Parameterized Edge Hamiltonicity

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    We study the parameterized complexity of the classical Edge Hamiltonian Path problem and give several fixed-parameter tractability results. First, we settle an open question of Demaine et al. by showing that Edge Hamiltonian Path is FPT parameterized by vertex cover, and that it also admits a cubic kernel. We then show fixed-parameter tractability even for a generalization of the problem to arbitrary hypergraphs, parameterized by the size of a (supplied) hitting set. We also consider the problem parameterized by treewidth or clique-width. Surprisingly, we show that the problem is FPT for both of these standard parameters, in contrast to its vertex version, which is W-hard for clique-width. Our technique, which may be of independent interest, relies on a structural characterization of clique-width in terms of treewidth and complete bipartite subgraphs due to Gurski and Wanke

    Partial Homology Relations - Satisfiability in terms of Di-Cographs

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    Directed cographs (di-cographs) play a crucial role in the reconstruction of evolutionary histories of genes based on homology relations which are binary relations between genes. A variety of methods based on pairwise sequence comparisons can be used to infer such homology relations (e.g.\ orthology, paralogy, xenology). They are \emph{satisfiable} if the relations can be explained by an event-labeled gene tree, i.e., they can simultaneously co-exist in an evolutionary history of the underlying genes. Every gene tree is equivalently interpreted as a so-called cotree that entirely encodes the structure of a di-cograph. Thus, satisfiable homology relations must necessarily form a di-cograph. The inferred homology relations might not cover each pair of genes and thus, provide only partial knowledge on the full set of homology relations. Moreover, for particular pairs of genes, it might be known with a high degree of certainty that they are not orthologs (resp.\ paralogs, xenologs) which yields forbidden pairs of genes. Motivated by this observation, we characterize (partial) satisfiable homology relations with or without forbidden gene pairs, provide a quadratic-time algorithm for their recognition and for the computation of a cotree that explains the given relations

    Advancing an interdisciplinary framework to study seed dispersal ecology

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    Although dispersal is generally viewed as a crucial determinant for the fitness of any organism, our understanding of its role in the persistence and spread of plant populations remains incomplete. Generalizing and predicting dispersal processes are challenging due to context dependence of seed dispersal, environmental heterogeneity and interdependent processes occurring over multiple spatial and temporal scales. Current population models often use simple phenomenological descriptions of dispersal processes, limiting their ability to examine the role of population persistence and spread, especially under global change. To move seed dispersal ecology forward, we need to evaluate the impact of any single seed dispersal event within the full spatial and temporal context of a plant’s life history and environmental variability that ultimately influences a population’s ability to persist and spread. In this perspective, we provide guidance on integrating empirical and theoretical approaches that account for the context dependency of seed dispersal to improve our ability to generalize and predict the consequences of dispersal, and its anthropogenic alteration, across systems. We synthesize suitable theoretical frameworks for this work and discuss concepts, approaches and available data from diverse subdisciplines to help operationalize concepts, highlight recent breakthroughs across research areas and discuss ongoing challenges and open questions. We address knowledge gaps in the movement ecology of seeds and the integration of dispersal and demography that could benefit from such a synthesis. With an interdisciplinary perspective, we will be able to better understand how global change will impact seed dispersal processes, and potential cascading effects on plant population persistence, spread and biodiversity

    Static and dynamic structure factors with account of the ion structure for high-temperature alkali and alkaline earth plasmas

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    The electron-electron, electron-ion, ion-ion and charge-charge static structure factors are calculated for alkali (at T = 30 000 K, 60 000 K, n (e) = 0.7 x 10(21) A center dot 1.1 x 10(22) cm(-3)) and Be2+ (at T = 20 eV, n (e) = 2.5 x 10(23) cm(-3)) plasmas using the method described by Gregori et al. The dynamic structure factors for alkali plasmas are calculated at T = 30 000 K, n (e) = 1.74 x 10(20), 1.11 x 10(22) cm(-3) using the method of moments developed by Adamjan et al. In both methods the screened Hellmann-Gurskii-Krasko potential, obtained on the basis of Bogolyubov's method, has been used taking into account not only the quantum-mechanical effects but also the repulsion due to the Pauli exclusion principle. The repulsive part of the Hellmann-Gurskii-Krasko (HGK) potential reflects important features of the ion structure. Our results on the static structure factors for Be2+ plasma deviate from the data obtained by Gregori et al., while our dynamic structure factors are in a reasonable agreement with those of Adamyan et al.: at higher values of k and with increasing k the curves damp down while at lower values of k, and especially at higher electron coupling, we observe sharp peaks also reported in the mentioned work. For lower electron coupling the dynamic structure factors of Li+, Na+, K+, Rb+ and Cs+ do not differ while at higher electron coupling these curves split. As the number of shell electrons increases from Li+ to Cs+ the curves shift in the direction of low absolute value of omega and their heights diminish. We conclude that the short range forces, which we take into account by means of the HGK model potential, which deviates from the Coulomb and Deutsch ones, influence the static and dynamic structure factors significantly.The work has been realised at the Humboldt University at Berlin (Germany). One of the authors (S. P. Sadykova) would like to express sincere thanks to the Erasmus Mundus Program of the EU for the financial support and especially to Mr. M. Parske for his aid, to the Institute of Physics, Humboldt University at Berlin, for the support which made her participation at some scientific Conferences possible; I. M. T. acknowledges the financial support of the Spanish Ministerio de Educacion y Ciencia Project No. ENE2007-67406-C02-02/FTN and valuable discussions with Dr. D. Gericke.Sadykova, SP.; Ebeling, W.; Tkachenko Gorski, IM. (2011). Static and dynamic structure factors with account of the ion structure for high-temperature alkali and alkaline earth plasmas. European Physical Journal D. 61(1):117-130. https://doi.org/10.1140/epjd/e2010-10118-yS117130611G. Gregori, O.L. Landen, S.H. Glenzer, Phys. Rev. E 74, 026402 (2006)G. Gregori, A. Ravasio, A. Höll, S.H. Glenzer, S.J. Rose, High Energy Density Physics 3, 99 (2007)V.M. Adamyan, I.M. Tkachenko, Teplofiz. Vys. Temp. 21, 417 (1983) [High Temp. (USA) 21, 307 (1983)]V.M. Adamyan, T. Meyer, I.M. Tkachenko, Fiz. Plazmy 11, 826 (1985) [Sov. J. Plasma Phys. 11, 481 (1985)]S.V. Adamjan, I.M. Tkachenko, J.L. Muñoz-Cobo, G. Verdú Martín, Phys. Rev. E 48, 2067 (1993)V.M. Adamyan, I.M. Tkachenko, Contrib. Plasma Phys. 43, 252 (2003)S. Sadykova, W. Ebeling, I. Valuev, I. Sokolov, Contrib. Plasma Phys. 49, 76 (2009)M.J. Rosseinsky, K. Prassides, Nature 464, 39 (2010)Physics and Chemistry of Alkali Metal Adsorption, edited by H.P. Bonzel, A.M. Bradshaw, G. Ertl (Elsevier, Amsterdam, 1989), Materials Science Monographs, Vol. 57A.N. Klyucharev, N.N. Bezuglov, A.A. Matveev, A.A. Mihajlov, Lj.M. Ignjatović, M.S. Dimitrijević, New Astron. Rev. 51, 547 (2007)F. Hensel, Liquid Metals, edited by R. Evans, D.A. Greenwood, IOP Conf. Ser. No. 30 (IPPS, London, 1977)F. Hensel, S. Juengst, F. Noll, R. Winter, In Localisation and Metal Insulator Transitions, edited by D. Adler, H. Fritsche (Plenum Press, New York, 1985)N.F. Mott, Metal-Insulator Transitions (Taylor and Francis, London, 1974)H. Hess, Physics of nonideal plasmas, edited by W. Ebeling, A. Foerster, R. Radtke, B.G. Teubner (Leipzig, 1992)V. Sizyuk, A. Hassanein, T. Sizyuk, J. Appl. Phys. 100, 103106 (2006)S. Sadykova, W. Ebeling, I. Valuev, I. Sokolov, Contrib. Plasma Phys. 49, 388 (2009)H. Ebert, Physikalisches Taschenbuch (F. Vieweg & Sohn, Braunschweig, 1967)S.H. Glenzer, G. Gregori, R.W. Lee, F.J. Rogers, S.W. Pollaine, O.L. Landen, Phys. Rev. Lett. 90, 175002 (2003)G. Gregori, S.H. Glenzer, H.-K. Chung, D.H. Froula, R.W. Lee, N.B. Meezan, J.D. Moody, C. Niemann, O.L. Landen, B. Holst, R. Redmer, S.P. Regan, H. Sawada, J. Quant. Spectrosc. Radiat. Transfer 99, 225237 (2006)D. Riley, N.C. Woolsey, D. McSherry, I. Weaver, A. Djaoui, E. Nardi, Phys. Rev. Lett. 84, 1704 (2000)S.H. Glenzer, Phys. Rev. Lett. 98, 065002 (2007)J. Sheffield, Plasma Scattering of Electromagnetic Radiation (Academic Press, New York, 1975)A. Höll, Th. Bornath, L. Cao, T. Döppner, S. Düsterer, E. Föster, C. Fortmann, S.H. Glenzer, G. Gregori, T. Laarmann, K.-H. Meiwes-Broer, A. Przystawik, P. Radcliffe, R. Redmer, H. Reinholz, G. Röpke, R. Thiele, J. Tiggesbäumker, S. Toleikis, N.X. Truong, T. Tschentscher, I. Ushmann, U. Zastrau, High Energy Density Phys. 3, 120 (2007)Yu.V. Arkhipov, A. Askaruly, D. Ballester, A.E. Davletov, G.M. Meirkhanova, I.M. Tkachenko, Phys. Rev. E 76, 026403 (2007)Yu.V. Arkhipov, A. Askaruly, D. Ballester, A.E. Davletov, I.M. Tkachenko, G. Zwicknagel, Phys. Rev. E 81, 026402 (2010)J.P. Hansen, I.R. Mc. Donald, Phys. Rev. A 23, 2041 (1981)J.P. Hansen, E.L. Polock, I.R. McDonald, Phys. Rev. Lett. 32, 277 (1974)V. Schwarz, B. Holst, T. Bornath, C. Fortmann, W-D. Kraeft, R. Thiele, R. Redmer, G. Gregori, H. Ja Leed, T. Döppner, S.H. Glenzer, High Energy Density Phys. 5, 1 (2009)D.O. Gericke, K. Wünsch, J. Vorberger, Nucl. Instrum. Methods Phys. Res. A 606, 142 (2009)B. Bernu, D. Ceperley, Quantum Monte Carlo Methods in Physics and Chemistry, edited by M.P. Nightingale, C. Umrigar (Kluwer Academic Publishers, Boston, 1999), NATO ASI Series, Series C, Mathematical and Physical Sciences, Vol. C-525G. Kelbg, Ann. Physik 13 354 (1964)C. Deutsch, Phys. Lett. A 60, 317 (1977)H. Minoo, M.M. Gombert, C. Deutsch, Phys. Rev. A 23, 924 (1981)W. Ebeling, G.E. Norman, A.A. Valuev, I. Valuev, Contrib. Plasma Phys. 39, 61 (1999)A.V. Filinov, M. Bonitz, W. Ebeling, J. Phys. A. 36, 5957 (2003)H. Hellmann, J. Chem. Phys. 3, 61 (1935)H. Hellmann, Acta Fizicochem. USSR 1, 913 (1935)H. Hellmann, Acta Fizicochem. USSR 4, 225 (1936)H. Hellmann, W. Kassatotschkin, Acta Fizicochem. USSR 5, 23 (1936)W.A. Harrison, Pseudopotentials in the Theory of Metals (Benjamin, New York, 1966)V. Heine, M.L. Cohen, D. Weaire, Psevdopotenzcial'naya Teoriya (Mir, Moskva, 1973)V. Heine, The pseudopotential concept, edited by H. Ehrenreich, F. Seitz, D. Turnbull, Solid State Physics 24, 1 (Academic, New York 1970)G.L. Krasko, Z.A. Gurskii, JETP Lett. 9, 363 (1969)W. Ebeling, W.-D. Kraeft, D. Kremp, Theory of Bound State and Ionization Equilibrium in Plasmas and Solids (Akademie-Verlag, Berlin, 1976)W. Zimdahl, W. Ebeling, Ann. Phys. (Leipzig) 34, 9 (1977)W. Ebeling, C.-V. Meister, R. Saendig, 13 ICPIG (Berlin, 1977) 725W. Ebeling, C.V. Meister, R. Saendig, W.-D. Kraeft, Ann. Phys. 491, 321 (1979)N.N. Bogolyubov, Dynamical Theory Problems in Statistical Physics (in Russian) (GITTL, Moscow, 1946)N.N. Bogolyubov, Studies in Statistical Mechanics, Engl. Transl., edited by J. De Boer, G.E. Uhlenbeck (North-Holland, Amsterdam, 1962)H. Falkenhagen, Theorie der Elektrolyte (S. Hirzel Verlag, Leipzig, 1971), p. 369Yu.V. Arkhipov, F.B. Baimbetov, A.E. Davletov, Eur. Phys. J. D 8, 299 (2000)P. Seuferling, J. Vogel, C. Toepffer, Phys. Rev. A 40, 323 (1989)L. Szasz, Pseudopotential Theory of Atoms and Molecules (Wiley-Intersc., New York, 1985)W.H.E. Schwarz, Acta Phys. Hung. 27, 391 (1969)W.H.E. Schwarz, Theor. Chim. Acta 11, 307 (1968)N.P. Kovalenko, Yu.P. Krasnyj, U. Krey, Physics of Amorphous Metalls (Wiley-VCH, Weinheim, 2001)Z.A. Gurski, G.L. Krasko, Doklady Akademii Nauk SSSR (in Russian) 197, 810 (1971)C. Fiolhais, J.P. Perdew, S.Q. Armster, J.M. MacLaren, Phys. Rev. B 51, 14001 (1995)S.S. Dalgic, S. Dalgic, G. Tezgor, Phys. Chem. Liq. 40, 539, (2002)E.M. Apfelbaum, Phys. Chem. Liq., 48, 534 (2010)Yu.V. Arkhipov, A.E. Davletov, Phys. Lett. A 247, 339 (1998)W. Ebeling, J. Ortner, Physica Scripta T 75, 93 (1998)J. Ortner, F. Schautz, W. Ebeling, Phys. Rev. E 56, 4665 (1997)N.I. Akhieser, The classical Moment Problem (Oliver and Boyd, London, 1965)M.G. Krein, A.A. Nudel'man, The Markov Moment Problem and External Problems (American Mathematical Society, Translations, New York, 1977)M.J. Corbatón, I.M. Tkachenko, Int. Conference on Strongly Coupled Coulomb Systems (SCCS2008), Camerino, Italy, July-August, 2008, Book of Abstracts, p. 90V.M. Adamyan, A.A. Mihajlov, N.M. Sakan, V.A. Srećković, I.M. Tkachenko, J. Phys. A: Math. Theor. 42, 214005 (2009)S. Ichimaru, Statistical Plasma Physics, Vol. I: Basic Principles (Addison-Wesley, Redwood City, 1992)W. Ebeling, A. Foerster, W. Richert, H. Hess, Physics A 150, 159 (1988)H. Wagenknecht, W. Ebeling, A. Förster, Contrib. Plasma Phys. 41, 15 (2001
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