A Nonliearly Dispersive Fifth Order Integrable Equation and its Hierarchy

In this paper, we study the properties of a nonlinearly dispersive integrable system of fifth order and its associated hierarchy. We describe a Lax representation for such a system which leads to two infinite series of conserved charges and two hierarchies of equations that share the same conserved charges. We construct two compatible Hamiltonian structures as well as their Casimir functionals. One of the structures has a single Casimir functional while the other has two. This allows us to extend the flows into negative order and clarifies the meaning of two different hierarchies of positive flows. We study the behavior of these systems under a hodograph transformation and show that they are related to the Kaup-Kupershmidt and the Sawada-Kotera equations under appropriate Miura transformations. We also discuss briefly some properties associated with the generalization of second, third and fourth order Lax operators.Comment: 11 pages, LaTex, version to be published in Journal of Nonlinear Mathematical Physics, has expanded discussio

Robotic control of the seven-degree-of-freedom NASA laboratory telerobotic manipulator

A computationally efficient robotic control scheme for the NASA Laboratory Telerobotic Manipulator (LTM) is presented. This scheme utilizes the redundancy of the seven-degree-of-freedom LTM to avoid joint limits and singularities. An analysis to determine singular configurations is presented. Performance criteria are determined based on the joint limits and singularity analysis. The control scheme is developed in the framework of resolved rate control using the gradient projection method, and it does not require the generalized inverse of the Jacobian. An efficient formulation for determining the joint velocities of the LTM is obtained. This control scheme is well suited for real-time implementation, which is essential if the end-effector trajectory is continuously modified based on sensory feedback. Implementation of this scheme on a Motorola 68020 VME bus-based controller of the LTM is in progress. Simulation results demonstrating the redundancy utilization in the robotic mode are presented

About the connection between vacuum birefringence and the light-light scattering amplitude

Birefringence phenomena stemming from vacuum polarization are revisited in the framework of coherent scattering. Based on photon-photon scattering, our analysis brings out the direct connection between this process and vacuum birefringence. We show how this procedure can be extended to the Kerr and the Cotton-Mouton birefringences in vacuum, thus providing a unified treatment of various polarization schemes, including those involving static fields

Florística e fitossociologia em áreas de manejo de açaizais no estuário amazônico.

Este estudo teve como objetivo analisar a composição florística e a fitossociologia em três regiões do estuário amazônico em que é praticado o manejo de açaizais nativos. Nas regiões foram instaladas 30 parcelas de 0,5 ha e amostradas todas as espécies arbóreas e palmeiras com DAP ? 5 cm, mediu-se também a circunferência a altura do peito (CAP) com fita métrica de precisão de 1mm. Foram inventariados 10821 indivíduos, representados por 114 espécies, 96 gêneros e 33 famílias. As famílias mais representativas foram Arecaceae (9 espécies e 8007 indivíduos), seguida por Rubiaceae (2 espécies e 522 indivíduos),Myristicaceae (1 espécie e 268 indivíduos), Malvaceae (10 espécies e 264 indivíduos) e Euphorbiaceae (4 espécies e 247 indivíduos). Constatou-se que a riqueza nas áreas de manejo inventariadas permaneceu alta apesar da pressão antrópica que essas áreas sofrem

Methods of Approximation in hpk Framework for ODEs in Time Resulting from Decoupling of Space and Time in IVPs

This is the published version. Copyright © 2011 Scientific Research PublishingThe present study considers mathematical classification of the time differential operators and then applies methods of approximation in time such as Galerkin method (GM ), Galerkin method with weak form (/GMWF ), Petrov-Galerkin method (PGM), weighted residual method (WRY ), and least squares method or process (LSM or LSP ) to construct finite element approximations in time. A correspondence is estab- lished between these integral forms and the elements of the calculus of variations: 1) to determine which methods of approximation yield unconditionally stable (variationally consistent integral forms, VC ) com- putational processes for which types of operators and, 2) to establish which integral forms do not yield un- conditionally stable computations (variationally inconsistent integral forms, VIC). It is shown that varia- tionally consistent time integral forms in hpk framework yield computational processes for ODEs in time that are unconditionally stable, provide a mechanism of higher order global differentiability approxima- tions as well as higher degree local approximations in time, provide control over approximation error when used as a time marching process and can indeed yield time accurate solutions of the evolution. Numerical studies are presented using standard model problems from the literature and the results are compared with Wilson’s method as well as Newmark method to demonstrate highly meritorious features of the pro- posed methodology

Placing community-based multiple-use forest management at the centre of the forest policy agenda.

Brazilian forestry law recognizes forests as public heritage for all citizens, and further recognizes their role in promoting social welfare for rural communities, which use and have domain of over 50% of Amazon public forests. However, there is a clear lack of public policies to support this notion. As such, a key issue for the community forestry sector is the need to focus on integration of traditional and technical knowledge and the promotion of institutional and local capacity of communities to manage these forests, and as such maintain in the long-term their economic and environmental goods and services. Rural education and training has a central role in the formation of a new generation of forest producers with management skills, though the response in terms of empowerment is slow, requiring at least a decade of investments. In the short-term, a transitional model is required to promote new arrangements in the relation between communities and businesses. With the government and civil society assuming a mediator role in the process to ensure a better balance between the private enterprise objective of maximizing profits, and the socio-environmental objectives of assuring participation of the local people in revenue distribution, and of minimizing impacts on biodiversity. Shared management is a crucial aspect for both the forest concession model, and for scaling up community forestry. Integration of forests into a new paradigm of economic development and social inclusion through their multiple use should consider the value of products and ecosystem services. Achieving this goal will depend on the capacity to promote local governance, negotiate the expansion of educational and infrastructure policies in the rural environment, and ensure the presence of technical assistance in the field. Finally, comes the need to foster responsible markets and consumers, linking forest products, environmental services and poverty alleviation in the tropical region.IUFRO17-624. Na publicação consta: Castro Euler, A. M.; Carneiro Guedes, M; Gazel Yared, J. A

Viking navigation

A comprehensive description of the navigation of the Viking spacecraft throughout their flight from Earth launch to Mars landing is given. The flight path design, actual inflight control, and postflight reconstruction are discussed in detail. The preflight analyses upon which the operational strategies and performance predictions were based are discussed. The inflight results are then discussed and compared with the preflight predictions and, finally, the results of any postflight analyses are presented

Implications of sea ice on Southern Ocean microseisms detected by a seismic array in West Antarctica

The proximity of Southern Ocean storms coupled with seasonal variation in sea ice make Antarctica ideal for the study of microseism sources. We explore frequency-dependent beamforming results using a short-duration, 60 km aperture, broad-band seismic array located on the Whillans Ice Stream, West Antarctica. Locations of single-frequency microseism (13–16 s period) generation are in regions where the continental shelf is ice-free, consistent with previous studies, and show Rayleigh wave sources remaining at consistent backazimuths throughout the duration of the array. Beamforming analysis of daily noise correlations shows that long-period double-frequency microseisms (9–11 s) consist predominantly of Rayleigh waves excited by storms in the Southern Ocean. Modelling of source locations based on wave–wave interaction provides a good fit to our data at these periods. We show that short-period double-frequency microseisms (5–7 s) in Antarctica consist of crustal phase Lg and body waves. Lg arrivals propagate through regions of continental crust and our data show that the Lg energy is generated when storm systems interact with the sea-ice-free continental shelf during austral summers. Ultra-short-period (0.3–2 s) microseismic body waves back project to regions that correlate with oceanic storm systems in both the Southern and Northern Hemispheres

Euler configurations and quasi-polynomial systems

In the Newtonian 3-body problem, for any choice of the three masses, there are exactly three Euler configurations (also known as the three Euler points). In Helmholtz' problem of 3 point vortices in the plane, there are at most three collinear relative equilibria. The "at most three" part is common to both statements, but the respective arguments for it are usually so different that one could think of a casual coincidence. By proving a statement on a quasi-polynomial system, we show that the "at most three" holds in a general context which includes both cases. We indicate some hard conjectures about the configurations of relative equilibrium and suggest they could be attacked within the quasi-polynomial framework.Comment: 21 pages, 6 figure

Coarse-grained entanglement classification through orthogonal arrays

Classification of entanglement in multipartite quantum systems is an open problem solved so far only for bipartite systems and for systems composed of three and four qubits. We propose here a coarse-grained classification of entanglement in systems consisting of $N$ subsystems with an arbitrary number of internal levels each, based on properties of orthogonal arrays with $N$ columns. In particular, we investigate in detail a subset of highly entangled pure states which contains all states defining maximum distance separable codes. To illustrate the methods presented, we analyze systems of four and five qubits, as well as heterogeneous tripartite systems consisting of two qubits and one qutrit or one qubit and two qutrits.Comment: 38 pages, 1 figur