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  • Engineering General  (2)
  • Models, Biological  (2)
  • *Conservation of Natural Resources/economics
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 17 (1993), S. 385-400 
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The equations governing the elastic-plastic deformation of granular materials are typically hyperbolic, or contain small-magnitude damping or rate effects. A finite element algorithm is the standard method for the numerical integration of these systems. In particular, finite elements allow great flexibility in the design of grid geometry. However, modern finite difference methods for hyperbolic systems have been successful in aerodynamics computations, resolving wave structures more sharply than finite element schemes. In this paper we develop a finite difference scheme for granular flow problems. We report on a second-order Godunov-type scheme for the integration of hyperbolic equations for the elastoplastic deformation of a simple model of granular flow. The Godunov method includes a characteristic tracing step in the integration, providing minimal wave dispersion, and a slope limiting step, preventing unphysical oscillations.The granular flow model we consider is hyperbolic, but hyperbolicity is lost at a large value of accumulated plastic strain. This loss of hyperbolicity is a tell-tale signal for the formation of a shear band within the sample. Typically, when systems lose hyperbolicity a regularization mechanism is added to the model equations in order to maintain the well posedness of the system. These regularizations include viscosity, viscoplasticity, higher-order gradient effects or stress coupling. Here we appeal to a very different kind of regularization. When the system loses hyperbolicity and a shear band forms, we treat the band as an internal boundary, and impose jump conditions at this boundary. Away from the band, the system remains hyperbolic and the integration step proceeds as usual.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 21 (1985), S. 779-787 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The eigenvalue problem for the Laplace operator is numerical investigated using the boundary integral equation (BIE) formulation. Three methods of discretization are given and illustrated with numerical examples.
    Additional Material: 4 Tab.
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 2002-11-02
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pitman, Nigel C A -- Jorgensen, Peter M -- New York, N.Y. -- Science. 2002 Nov 1;298(5595):989.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Tropical Conservation, Box 90381, Duke University, Durham, NC 27708-0381, USA. ncp@duke.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12411696" target="_blank"〉PubMed〈/a〉
    Keywords: Budgets ; *Conservation of Natural Resources/economics ; Costs and Cost Analysis ; *Ecosystem ; *Plants ; *Tropical Climate
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2013-10-19
    Description: The vast extent of the Amazon Basin has historically restricted the study of its tree communities to the local and regional scales. Here, we provide empirical data on the commonness, rarity, and richness of lowland tree species across the entire Amazon Basin and Guiana Shield (Amazonia), collected in 1170 tree plots in all major forest types. Extrapolations suggest that Amazonia harbors roughly 16,000 tree species, of which just 227 (1.4%) account for half of all trees. Most of these are habitat specialists and only dominant in one or two regions of the basin. We discuss some implications of the finding that a small group of species--less diverse than the North American tree flora--accounts for half of the world's most diverse tree community.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉ter Steege, Hans -- Pitman, Nigel C A -- Sabatier, Daniel -- Baraloto, Christopher -- Salomao, Rafael P -- Guevara, Juan Ernesto -- Phillips, Oliver L -- Castilho, Carolina V -- Magnusson, William E -- Molino, Jean-Francois -- Monteagudo, Abel -- Nunez Vargas, Percy -- Montero, Juan Carlos -- Feldpausch, Ted R -- Coronado, Euridice N Honorio -- Killeen, Tim J -- Mostacedo, Bonifacio -- Vasquez, Rodolfo -- Assis, Rafael L -- Terborgh, John -- Wittmann, Florian -- Andrade, Ana -- Laurance, William F -- Laurance, Susan G W -- Marimon, Beatriz S -- Marimon, Ben-Hur Jr -- Guimaraes Vieira, Ima Celia -- Amaral, Ieda Leao -- Brienen, Roel -- Castellanos, Hernan -- Cardenas Lopez, Dairon -- Duivenvoorden, Joost F -- Mogollon, Hugo F -- Matos, Francisca Dionizia de Almeida -- Davila, Nallarett -- Garcia-Villacorta, Roosevelt -- Stevenson Diaz, Pablo Roberto -- Costa, Flavia -- Emilio, Thaise -- Levis, Carolina -- Schietti, Juliana -- Souza, Priscila -- Alonso, Alfonso -- Dallmeier, Francisco -- Montoya, Alvaro Javier Duque -- Fernandez Piedade, Maria Teresa -- Araujo-Murakami, Alejandro -- Arroyo, Luzmila -- Gribel, Rogerio -- Fine, Paul V A -- Peres, Carlos A -- Toledo, Marisol -- Aymard C, Gerardo A -- Baker, Tim R -- Ceron, Carlos -- Engel, Julien -- Henkel, Terry W -- Maas, Paul -- Petronelli, Pascal -- Stropp, Juliana -- Zartman, Charles Eugene -- Daly, Doug -- Neill, David -- Silveira, Marcos -- Paredes, Marcos Rios -- Chave, Jerome -- Lima Filho, Diogenes de Andrade -- Jorgensen, Peter Moller -- Fuentes, Alfredo -- Schongart, Jochen -- Cornejo Valverde, Fernando -- Di Fiore, Anthony -- Jimenez, Eliana M -- Penuela Mora, Maria Cristina -- Phillips, Juan Fernando -- Rivas, Gonzalo -- van Andel, Tinde R -- von Hildebrand, Patricio -- Hoffman, Bruce -- Zent, Eglee L -- Malhi, Yadvinder -- Prieto, Adriana -- Rudas, Agustin -- Ruschell, Ademir R -- Silva, Natalino -- Vos, Vincent -- Zent, Stanford -- Oliveira, Alexandre A -- Schutz, Angela Cano -- Gonzales, Therany -- Trindade Nascimento, Marcelo -- Ramirez-Angulo, Hirma -- Sierra, Rodrigo -- Tirado, Milton -- Umana Medina, Maria Natalia -- van der Heijden, Geertje -- Vela, Cesar I A -- Vilanova Torre, Emilio -- Vriesendorp, Corine -- Wang, Ophelia -- Young, Kenneth R -- Baider, Claudia -- Balslev, Henrik -- Ferreira, Cid -- Mesones, Italo -- Torres-Lezama, Armando -- Urrego Giraldo, Ligia Estela -- Zagt, Roderick -- Alexiades, Miguel N -- Hernandez, Lionel -- Huamantupa-Chuquimaco, Isau -- Milliken, William -- Palacios Cuenca, Walter -- Pauletto, Daniela -- Valderrama Sandoval, Elvis -- Valenzuela Gamarra, Luis -- Dexter, Kyle G -- Feeley, Ken -- Lopez-Gonzalez, Gabriela -- Silman, Miles R -- New York, N.Y. -- Science. 2013 Oct 18;342(6156):1243092. doi: 10.1126/science.1243092.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Naturalis Biodiversity Center, Leiden, Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24136971" target="_blank"〉PubMed〈/a〉
    Keywords: *Biodiversity ; Models, Biological ; Population ; *Rivers ; South America ; Trees/*classification/*physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2002-01-26
    Description: The high alpha-diversity of tropical forests has been amply documented, but beta-diversity-how species composition changes with distance-has seldom been studied. We present quantitative estimates of beta-diversity for tropical trees by comparing species composition of plots in lowland terra firme forest in Panama, Ecuador, and Peru. We compare observations with predictions derived from a neutral model in which habitat is uniform and only dispersal and speciation influence species turnover. We find that beta-diversity is higher in Panama than in western Amazonia and that patterns in both areas are inconsistent with the neutral model. In Panama, habitat variation appears to increase species turnover relative to Amazonia, where unexpectedly low turnover over great distances suggests that population densities of some species are bounded by as yet unidentified processes. At intermediate scales in both regions, observations can be matched by theory, suggesting that dispersal limitation, with speciation, influences species turnover.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Condit, Richard -- Pitman, Nigel -- Leigh, Egbert G Jr -- Chave, Jerome -- Terborgh, John -- Foster, Robin B -- Nunez, Percy -- Aguilar, Salomon -- Valencia, Renato -- Villa, Gorky -- Muller-Landau, Helene C -- Losos, Elizabeth -- Hubbell, Stephen P -- New York, N.Y. -- Science. 2002 Jan 25;295(5555):666-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Tropical Forest Science, Smithsonian Tropical Research Institute, Unit 0948, APO AA 34002-0948, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11809969" target="_blank"〉PubMed〈/a〉
    Keywords: *Ecosystem ; Ecuador ; Environment ; Fourier Analysis ; Models, Biological ; Panama ; Peru ; Probability ; *Trees/classification/growth & development ; *Tropical Climate
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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