16,800 research outputs found

    A Kam Theorem for Space-Multidimensional Hamiltonian PDE

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    We present an abstract KAM theorem, adapted to space-multidimensional hamiltonian PDEs with smoothing non-linearities. The main novelties of this theorem are that: \bullet the integrable part of the hamiltonian may contain a hyperbolic part and as a consequence the constructed invariant tori may be unstable. \bullet It applies to singular perturbation problem. In this paper we state the KAM-theorem and comment on it, give the main ingredients of the proof, and present three applications of the theorem .Comment: arXiv admin note: text overlap with arXiv:1502.0226

    Chromatographic test facility. Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration

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    Test facility to verify design concepts and mathematical models of chromatograph for atmospheric composition analysis of Mar

    Photosynthetic Gas Exchange in the Closed Ecosystem for Space. Phase II, Part III. Screening for Thermophilic Algae and Mutation Studies

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    An algal screening and mutation study was undertaken to obtain algae superior to Chlorella 71105 for use in a photosynthetic gas exchanger. Of the forty-four thermophilic algae studied, eighteen appeared to have growth rates as great as Chlorella 71105. Optimization of the physical and chemical environments of these strains is recommended as a way to further improve growth rates and concomitant oxygen production. The mutation study revealed that Chlorella 71105 is relatively resistant to germicidal ultraviolet radiation. No high temperature mutants of Chlorella 71105 were found

    Single nanoparticle measurement techniques

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    Various single particle measuring techniques are briefly reviewed and the basic concepts of a new micro-SQUID technique are discussed. It allows measurements of the magnetization reversal of single nanometer-sized particles at low temperature. The influence of the measuring technique on the system of interest is discussed.Comment: 3 pages, 3 figures, conference proceedings of MMM 1999, San Jose, 15-18 Nov., session number BE-0

    SYGMA: Stellar Yields for Galactic Modeling Applications

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    The stellar yields for galactic modeling applications (SYGMA) code is an open-source module that models the chemical ejecta and feedback of simple stellar populations (SSPs). It is intended for use in hydrodynamical simulations and semi-analytic models of galactic chemical evolution. The module includes the enrichment from asymptotic giant branch (AGB) stars, massive stars, SNIa and neutron-star mergers. An extensive and extendable stellar yields library includes the NuGrid yields with all elements and many isotopes up to Bi. Stellar feedback from mechanic and frequency-dependent radiative luminosities are computed based on NuGrid stellar models and their synthetic spectra. The module further allows for customizable initial-mass functions and supernova Ia (SNIa) delay-time distributions to calculate time-dependent ejecta based on stellar yield input. A variety of r-process sites can be included. A comparison of SSP ejecta based on NuGrid yields with those from Portinari et al. (1998) and Marigo (2001) reveals up to a factor of 3.5 and 4.8 less C and N enrichment from AGB stars at low metallicity, a result we attribute to NuGrid's modeling of hot-bottom burning. Different core-collapse supernova explosion and fallback prescriptions may lead to substantial variations for the accumulated ejecta of C, O and Si in the first 107yr10^7\, \mathrm{yr} at Z=0.001Z=0.001. An online interface of the open-source SYGMA module enables interactive simulations, analysis and data extraction of the evolution of all species formed by the evolution of simple stellar populations.Comment: 18 pages, 10 figures, 3 tables, published in ApJ

    Optimization of Single-Sided Charge-Sharing Strip Detectors

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    Simulation of the charge sharing properties of single-sided CZT strip detectors with small anode pads are presented. The effect of initial event size, carrier repulsion, diffusion, drift, trapping and detrapping are considered. These simulations indicate that such a detector with a 150 µm pitch will provide good charge sharing between neighboring pads. This is supported by a comparison of simulations and measurements for a similar detector with a coarser pitch of 225 µm that could not provide sufficient sharing. The performance of such a detector used as a gamma-ray imager is discussed
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