1,263 research outputs found

    Unsupported thin film beam splitter

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    Multilayer beam splitter system yielding nearly equal broadband infrared reflectance and transmittance in the 5 to 50 micron spectral region has been developed which will significantly reduce size and cost of light path compensating devices in infrared spectral instruments

    Multilayer infrared beamsplitter film system

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    Multilayer infrared beamsplitter film system on a potassium bromide crystal substrate is operational over a wavelength range of 2.5 to 25 microns with nearly equal broadband reflectance and transmittance. It is useful in optical coating, vacuum deposition, radiometry, interferometry, and spectrometry

    High efficiency optical beamsplitter designed for operation in the infrared region

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    Beamsplitter system uses potassium bromide as substrate for operating in the spectral region between 5 and 30 microns and calcium fluoride for narrowband applications. It uses a 13-layer film which yields nearly equal broadband infrared reflectance and transmittance

    Curation of Frozen Samples

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    NASA's Johnson Space Center (JSC) and the Astromaterials Curator are charged by NPD 7100.10D with the curation of all of NASA s extraterrestrial samples, including those from future missions. This responsibility includes the development of new sample handling and preparation techniques; therefore, the Astromaterials Curator must begin developing procedures to preserve, prepare and ship samples at sub-freezing temperatures in order to enable future sample return missions. Such missions might include the return of future frozen samples from permanently-shadowed lunar craters, the nuclei of comets, the surface of Mars, etc. We are demonstrating the ability to curate samples under cold conditions by designing, installing and testing a cold curation glovebox. This glovebox will allow us to store, document, manipulate and subdivide frozen samples while quantifying and minimizing contamination throughout the curation process

    A Hierarchical Recurrent Encoder-Decoder For Generative Context-Aware Query Suggestion

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    Users may strive to formulate an adequate textual query for their information need. Search engines assist the users by presenting query suggestions. To preserve the original search intent, suggestions should be context-aware and account for the previous queries issued by the user. Achieving context awareness is challenging due to data sparsity. We present a probabilistic suggestion model that is able to account for sequences of previous queries of arbitrary lengths. Our novel hierarchical recurrent encoder-decoder architecture allows the model to be sensitive to the order of queries in the context while avoiding data sparsity. Additionally, our model can suggest for rare, or long-tail, queries. The produced suggestions are synthetic and are sampled one word at a time, using computationally cheap decoding techniques. This is in contrast to current synthetic suggestion models relying upon machine learning pipelines and hand-engineered feature sets. Results show that it outperforms existing context-aware approaches in a next query prediction setting. In addition to query suggestion, our model is general enough to be used in a variety of other applications.Comment: To appear in Conference of Information Knowledge and Management (CIKM) 201

    A Numerical Method to Compute Brain Injury Associated to Concussion

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    This research proposes a new a numerical method to compute brain injury associated with concussion using the Peak Virtual Power method, using the THUMS 4.02 head model. The results indicate that mild and severe concussions could be prevented for lateral collisions and frontal impacts with PVP values lower than 0.928mW and 9.405mW, respectively, and no concussion would happen in the head vertical direction for a PVP value less than 1.184mW. This innovative method proposes a new paradigm to improve helmet designs, assess sports injuries and improve people's wellbeing.Comment: 12 page

    Ring Formation in Magnetically Subcritical Clouds and Multiple Star Formation

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    We study numerically the ambipolar diffusion-driven evolution of non-rotating, magnetically subcritical, disk-like molecular clouds, assuming axisymmetry. Previous similar studies have concentrated on the formation of single magnetically supercritical cores at the cloud center, which collapse to form isolated stars. We show that, for a cloud with many Jeans masses and a relatively flat mass distribution near the center, a magnetically supercritical ring is produced instead. The supercritical ring contains a mass well above the Jeans limit. It is expected to break up, through both gravitational and possibly magnetic interchange instabilities, into a number of supercritical dense cores, whose dynamic collapse may give rise to a burst of star formation. Non-axisymmetric calculations are needed to follow in detail the expected ring fragmentation into multiple cores and the subsequent core evolution. Implications of our results on multiple star formation in general and the northwestern cluster of protostars in the Serpens molecular cloud core in particular are discussed.Comment: 25 pages, 4 figures, to appear in Ap

    A Numerical Method to Compute Brain Injury Associated to Concussion

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    This research proposes a new a numerical method to compute brain injury associated with concussion using the Peak Virtual Power method, using the THUMS 4.02 head model. The results indicate that mild and severe concussions could be prevented for lateral collisions and frontal impacts with PVP values lower than 0.928mW and 9.405mW, respectively, and no concussion would happen in the head vertical direction for a PVP value less than 1.184mW. This innovative method proposes a new paradigm to improve helmet designs, assess sports injuries and improve people's wellbeing.Comment: 12 page

    An implicit method for radiative transfer with the diffusion approximation in SPH

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    An implicit method for radiative transfer in SPH is described. The diffusion approximation is used, and the hydrodynamic calculations are performed by a fully three--dimensional SPH code. Instead of the energy equation of state for an ideal gas, various energy states and the dissociation of hydrogen molecules are considered in the energy calculation for a more realistic temperature and pressure determination. In order to test the implicit code, we have performed non--isothermal collapse simulations of a centrally condensed cloud, and have compared our results with those of finite difference calculations performed by MB93. The results produced by the two completely different numerical methods agree well with each other.Comment: 25 pages, 9 figure
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