3,242 research outputs found

    Data compression for near Earth and deep space to Earth transmission

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    Key issues of data compression for near Earth and deep space to Earth transmission discussion group are briefly presented. Specific recommendations as made by the group are as follows: (1) since data compression is a cost effective way to improve communications and storage capacity, NASA should use lossless data compression wherever possible; (2) NASA should conduct experiments and studies on the value and effectiveness of lossy data compression; (3) NASA should develop and select approaches to high ratio compression of operational data such as voice and video; (4) NASA should develop data compression integrated circuits for a few key approaches identified in the preceding recommendation; (5) NASA should examine new data compression approaches such as combining source and channel encoding, where high payoff gaps are identified in currently available schemes; and (6) users and developers of data compression technologies should be in closer communication within NASA and with academia, industry, and other government agencies

    A System for Acquiring, Processing, and Rendering Panoramic Light Field Stills for Virtual Reality

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    We present a system for acquiring, processing, and rendering panoramic light field still photography for display in Virtual Reality (VR). We acquire spherical light field datasets with two novel light field camera rigs designed for portable and efficient light field acquisition. We introduce a novel real-time light field reconstruction algorithm that uses a per-view geometry and a disk-based blending field. We also demonstrate how to use a light field prefiltering operation to project from a high-quality offline reconstruction model into our real-time model while suppressing artifacts. We introduce a practical approach for compressing light fields by modifying the VP9 video codec to provide high quality compression with real-time, random access decompression. We combine these components into a complete light field system offering convenient acquisition, compact file size, and high-quality rendering while generating stereo views at 90Hz on commodity VR hardware. Using our system, we built a freely available light field experience application called Welcome to Light Fields featuring a library of panoramic light field stills for consumer VR which has been downloaded over 15,000 times.Comment: 15 pages, 14 figures, 2 tables, accepted by SIGGRAPH Asia 2018, low-resolution versio

    Families of Bianchi modular symbols: critical base-change p-adic L-functions and p-adic Artin formalism

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    Let KK be an imaginary quadratic field. In this article, we study the eigenvariety for GL(2)/K, proving an etaleness result for the weight map at non-critical classical points and a smoothness result at base-change classical points. We give three main applications of this; let ff be a regular pp-stabilised newform of weight kk at least 2 without CM by KK. (1) We construct a two-variable pp-adic LL-function attached to the base-change of ff to KK under assumptions on ff that we conjecture always hold, in particular making no assumption on the slope of ff. (2) We construct three-variable pp-adic LL-functions over the eigenvariety interpolating the pp-adic LL-functions of classical base-change Bianchi cusp forms in families. (3) We prove that these base-change pp-adic LL-functions satisfy a pp-adic Artin formalism result, that is, they factorise in the same way as the classical LL-function under Artin formalism. In an appendix, Carl Wang-Erickson describes a base-change deformation functor and gives a characterisation of its Zariski tangent space.Comment: 26 pages, with a 3 page appendix by Carl Wang-Erickson. Comments welcome! Changes for v5: added contents, minor changes to exposition. v4: corrected funding acknowledgements. v3: This version has a new introduction, has been reorganised and greatly shortened, and incorporates minor corrections. v2: minor correction

    Some acoustic and articulatory correlates of phrasal stress in Spanish

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    All spoken languages show rhythmic patterns. Recent work with a number of different languages (English, Japanese, Mandarin Chinese, and French) suggests that metrically (hierarchically) assigned stress levels of the utterance show strong correlations with the amount of jaw displacement, and corresponding F1 values. This paper examines some articulatory and acoustic correlates of Spanish rhythm; specifically, we ask if there is a correlation between phrasal stress values metrically assigned to each syllable and acoustic/articulatory values. We used video recordings of three Salvadoran Spanish speakers to measure maximum jaw displacement, mean F0, mean intensity, mean duration, and mid-vowel F1 for each vowel in two Spanish sentences. The results show strong correlations between stress and duration, and between stress and F1, but weak correlations between stress and both mean vowel intensity and maximum jaw displacement. We also found weak correlations between jaw displacement and both mean vowel intensity and F1

    LSP Composite Susbtrate Destructive Evaluation Test Assessment Manual

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    This document specifies the processes to perform post-strike destructive damage evaluation of tested CFRP panels.It is recognized that many factors besides lightning damage protection are involved in the selection of an appropriate Lightning Strike Protection (LSP) for a particular system (e.g., cost, weight, corrosion resistance, shielding effectiveness, etc.). This document strives primarily to address the standardized generation of damage protection performance data

    A high resolution line survey of IRC+10216 with Herschel. First results: Detection of warm silicon dicarbide SiC2

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    We present the first results of a high-spectral-resolution survey of the carbon-rich evolved star IRC+10216 that was carried out with the HIFI spectrometer onboard Herschel. This survey covers all HIFI bands, with a spectral range from 488 to 1901GHz. In this letter we focus on the band-1b spectrum, in a spectral range 554.5-636.5GHz, where we identified 130 spectral features with intensities above 0.03 K and a signal-to-noise ratio >5. Detected lines arise from HCN, SiO, SiS, CS, CO, metal-bearing species and, surprisingly, silicon dicarbide (SiC2). We identified 55 SiC2 transitions involving energy levels between 300 and 900 K. By analysing these rotational lines, we conclude that SiC2 is produced in the inner dust formation zone, with an abundance of ~2x10^-7 relative to molecular hydrogen. These SiC2 lines have been observed for the first time in space and have been used to derive an SiC2 rotational temperature of ~204 K and a source-averaged column density of ~6.4x10^15 cm^-2. Furthermore, the high quality of the HIFI data set was used to improve the spectroscopic rotational constants of SiC2.Comment: A&A HIFI Special Issue, 201
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