1,154 research outputs found

    Part I: General Considerations of Radiant Energy: Radiation Problems Related to Space Flight

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    Paper Session II-B - National Launch System Payload Accommodations

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    Early definition, documentation, acceptance, and continuing implementation of a standard system of payload accommodations for space launch systems is essential. Attempts to provide truly standard payload accommodations have not met with significant success in increasing responsiveness or reducing operations costs. The operational philosophy of the National Launch System (NLS) is based on standardization and includes standardized payload accommodations. These must be incorporated into NLS design concepts early in the development phase to ensure the NLS goal of increased responsiveness and reduced operating cost. At the same time, sufficient flexibility will be maintained to accommodate the rare unique payload requirement which cannot meet the standard due to specific mission requirements, safety concerns, or other reasons. Definition of payload accommodation design goals and operational employment scenarios, and their rationale, will be described, as well as methods for ensuring payload community acceptance and continued implementation

    Needle Variation in Loblolly Pine from Mesic and Xeric Seed Sources

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    Anatomical modifications in protective layers and stomatal characteristics of needles which would have moisture conserving effects were found in 2-yr-old seedlings of 1oblolly pines of the Bastrop County, Texas, provenance. Most of these modifications were absent from needles of 16-yr-old trees of the same provenance. Forest Sci. 20:88-90

    Cluster Approximation for the Farey Fraction Spin Chain

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    We consider the Farey fraction spin chain in an external field hh. Utilising ideas from dynamical systems, the free energy of the model is derived by means of an effective cluster energy approximation. This approximation is valid for divergent cluster sizes, and hence appropriate for the discussion of the magnetizing transition. We calculate the phase boundaries and the scaling of the free energy. At h=0h=0 we reproduce the rigorously known asymptotic temperature dependence of the free energy. For h≠0h \ne 0, our results are largely consistent with those found previously using mean field theory and renormalization group arguments.Comment: 17 pages, 3 figure

    Ramanujan sums for signal processing of low frequency noise

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    An aperiodic (low frequency) spectrum may originate from the error term in the mean value of an arithmetical function such as M\"obius function or Mangoldt function, which are coding sequences for prime numbers. In the discrete Fourier transform the analyzing wave is periodic and not well suited to represent the low frequency regime. In place we introduce a new signal processing tool based on the Ramanujan sums c_q(n), well adapted to the analysis of arithmetical sequences with many resonances p/q. The sums are quasi-periodic versus the time n of the resonance and aperiodic versus the order q of the resonance. New results arise from the use of this Ramanujan-Fourier transform (RFT) in the context of arithmetical and experimental signalsComment: 11 pages in IOP style, 14 figures, 2 tables, 16 reference

    Modeling the CO2-effects of forest management and wood usage on a regional basis

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    BACKGROUND: At the 15(th) Conference of Parties of the UN Framework Convention on Climate Change, Copenhagen, 2009, harvested wood products were identified as an additional carbon pool. This modification eliminates inconsistencies in greenhouse gas reporting by recognizing the role of the forest and timber sector in the global carbon cycle. Any additional CO(2)-effects related to wood usage are not considered by this modification. This results in a downward bias when the contribution of the forest and timber sector to climate change mitigation is assessed. The following article analyses the overall contribution to climate protection made by the forest management and wood utilization through CO(2)-emissions reduction using an example from the German state of North Rhine-Westphalia. Based on long term study periods (2011 to 2050 and 2100, respectively). Various alternative scenarios for forest management and wood usage are presented. RESULTS: In the mid- to long-term (2050 and 2100, respectively) the net climate protection function of scenarios with varying levels of wood usage is higher than in scenarios without any wood usage. This is not observed for all scenarios on short and mid term evaluations. The advantages of wood usage are evident although the simulations resulted in high values for forest storage in the C pools. Even the carbon sink effect due to temporal accumulation of deadwood during the period from 2011 to 2100 is outbalanced by the potential of wood usage effects. CONCLUSIONS: A full assessment of the CO(2)-effects of the forest management requires an assessment of the forest supplemented with an assessment of the effects of wood usage. CO(2)-emission reductions through both fuel and material substitution as well as CO(2) sink in wood products need to be considered. An integrated assessment of the climate protection function based on the analysis of the study’s scenarios provides decision parameters for a strategic approach to climate protection with regard to forest management and wood use at regional and national levels. The short-term evaluation of subsystems can be misleading, rendering long-term evaluations (until 2100, or even longer) more effective. This is also consistent with the inherently long-term perspective of forest management decisions and measures

    Symbolic dynamics for the NN-centre problem at negative energies

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    We consider the planar NN-centre problem, with homogeneous potentials of degree -\a<0, \a \in [1,2). We prove the existence of infinitely many collisions-free periodic solutions with negative and small energy, for any distribution of the centres inside a compact set. The proof is based upon topological, variational and geometric arguments. The existence result allows to characterize the associated dynamical system with a symbolic dynamics, where the symbols are the partitions of the NN centres in two non-empty sets

    Entropy Distance: New Quantum Phenomena

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    We study a curve of Gibbsian families of complex 3x3-matrices and point out new features, absent in commutative finite-dimensional algebras: a discontinuous maximum-entropy inference, a discontinuous entropy distance and non-exposed faces of the mean value set. We analyze these problems from various aspects including convex geometry, topology and information geometry. This research is motivated by a theory of info-max principles, where we contribute by computing first order optimality conditions of the entropy distance.Comment: 34 pages, 5 figure

    On the Form Factor for the Unitary Group

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    We study the combinatorics of the contributions to the form factor of the group U(N) in the large NN limit. This relates to questions about semiclassical contributions to the form factor of quantum systems described by the unitary ensemble.Comment: 35 page
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