3,538 research outputs found

    Lean Six Sigma and Assurance of Learning: Challenges and Opportunities

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    The importance, and associated challenges, of faculty ownership and engagement in the assurance of learning (AoL) process are well documented in the literature. The authors demonstrate how schools can further their AoL objectives by encouraging and subsequently supporting organic, faculty-led initiatives. Specifically, we present a case study of a faculty led initiative to explore and demonstrate, as a proof of concept, how Lean Six Sigma can be used to improve AoL practices

    Statistical Orbit Determination using the Particle Filter for Incorporating Non-Gaussian Uncertainties

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    The tracking of space objects requires frequent and accurate monitoring for collision avoidance. As even collision events with very low probability are important, accurate prediction of collisions require the representation of the full probability density function (PDF) of the random orbit state. Through representing the full PDF of the orbit state for orbit maintenance and collision avoidance, we can take advantage of the statistical information present in the heavy tailed distributions, more accurately representing the orbit states with low probability. The classical methods of orbit determination (i.e. Kalman Filter and its derivatives) provide state estimates based on only the second moments of the state and measurement errors that are captured by assuming a Gaussian distribution. Although the measurement errors can be accurately assumed to have a Gaussian distribution, errors with a non-Gaussian distribution could arise during propagation between observations. Moreover, unmodeled dynamics in the orbit model could introduce non-Gaussian errors into the process noise. A Particle Filter (PF) is proposed as a nonlinear filtering technique that is capable of propagating and estimating a more complete representation of the state distribution as an accurate approximation of a full PDF. The PF uses Monte Carlo runs to generate particles that approximate the full PDF representation. The PF is applied in the estimation and propagation of a highly eccentric orbit and the results are compared to the Extended Kalman Filter and Splitting Gaussian Mixture algorithms to demonstrate its proficiency

    The Abacus Cosmos: A Suite of Cosmological N-body Simulations

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    We present a public data release of halo catalogs from a suite of 125 cosmological NN-body simulations from the Abacus project. The simulations span 40 wwCDM cosmologies centered on the Planck 2015 cosmology at two mass resolutions, 4×1010  h−1M⊙4\times 10^{10}\;h^{-1}M_\odot and 1×1010  h−1M⊙1\times 10^{10}\;h^{-1}M_\odot, in 1.1  h−1Gpc1.1\;h^{-1}\mathrm{Gpc} and 720  h−1Mpc720\;h^{-1}\mathrm{Mpc} boxes, respectively. The boxes are phase-matched to suppress sample variance and isolate cosmology dependence. Additional volume is available via 16 boxes of fixed cosmology and varied phase; a few boxes of single-parameter excursions from Planck 2015 are also provided. Catalogs spanning z=1.5z=1.5 to 0.10.1 are available for friends-of-friends and Rockstar halo finders and include particle subsamples. All data products are available at https://lgarrison.github.io/AbacusCosmosComment: 13 pages, 9 figures, 3 tables. Additional figures added for mass resolution convergence tests, and additional redshifts added for existing tests. Matches ApJS accepted versio

    Prospects for commercialization of SELV-based in-space operations

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    A workshop was hosted by the Langley Research Center as a part of an activity to assess the commercialization potential of Small Expendible Launch Vehicle-based in-space operations. Representatives of the space launch insurance industry, industrial consultants, producers of spacecraft, launch vehicle manufacturers, and government researchers constituted the participants. The workshop was broken into four sessions: Customers Small Expendible Launch Systems, Representative Missions, and Synthesis-Government role. This publication contains the presentation material, written synopses of the sessions, and conclusions developed at the workshop

    Autonomous rendezvous and docking for Space Station Freedom

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    Viewgraphs on autonomous rendezvous and docking (AR&D) for Space Station Freedom are presented. Topics covered include: requirements for AR&D experience; Comet spacecraft performance; AR&D mission profile; analytical models for approach trajectory, loosely coupled configuration, and contact dynamics; and application to space infrastructure

    Transverse multi-mode effects on the performance of photon-photon gates

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    The multi-mode character of quantum fields imposes constraints on the implementation of high-fidelity quantum gates between individual photons. So far this has only been studied for the longitudinal degree of freedom. Here we show that effects due to the transverse degrees of freedom significantly affect quantum gate performance. We also discuss potential solutions, in particular separating the two photons in the transverse direction.Comment: 5 pages, 3 figures, published versio

    Sputtering of benzene sample by large Ne, Ar and Kr clusters : molecular dynamics computer simulations

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    Molecular dynamics simulations are employed to probe the role of an impact angle on emission efficiency of organic molecules sputtered from benzene crystal bombarded by 15 keV Ne2953Ne_{2953}, Ar2953Ar_{2953}, and Kr2953Kr_{2953} clusters. It is found that both the cluster type and the angle of incidence have significant effect on the emission efficiency. The shape of the impact angle dependence does not resemble the dependence characteristic for medium size clusters (C60,Ar366C_{60}, Ar_{366}), where sputtering yield only moderately increases with the impact angle, has a shallow maximum around 40° and then decreases. On the contrary, for the large projectiles (Ne2953,Ar2953Ne_{2953}, Ar_{2953}, and Kr2953Kr_{2953}) the emission efficiency steeply increases with the impact angle, has a pronounced maximum around 55° followed by rapid signal decay. It has been found that the sputtering yield is the most sensitive to the impact angle change for Kr cluster projectiles, while change of the impact angle of Ne projectile has the smallest effect on the efficiency of material ejection

    Cross-Kerr nonlinearity between continuous-mode coherent states and single photons

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    Weak cross-Kerr nonlinearities between single photons and coherent states are the basis for many applications in quantum information processing. These nonlinearities have so far mainly been discussed in terms of highly idealized single-mode models. We develop a general theory of the interaction between continuous-mode photonic pulses and apply it to the case of a single photon interacting with a coherent state. We quantitatively study the validity of the usual single-mode approximation using the concepts of fidelity and conditional phase. We show that high fidelities, non-zero conditional phases and high photon numbers are compatible, under conditions where the pulses fully pass through each other and where unwanted transverse-mode effects are suppressed.Comment: 8 pages, 2 figures, more general results in section V

    Ocean Wind Speed Measurement Using Wideband GNSS-R Signals

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    The use of Global Navigation Satellite System-Reflectometry (GNSS-R) for remote sensing of ocean wind speeds has been explored for nearly two decades and has become an important passive remote sensing technique for verification of hurricane formation models. To obtain wind speed measurements, reflected GNSS signals are first cross-correlated with locally generated copies to construct delay-doppler maps (DDMs). Through statistical models, DDMs can provide information about the mean-square slope (MSS) of the ocean surface, which is related to wind speed. Previous studies have focused on legacy signals such as GPS L1. However, it is expected that the MSS relationship with ocean wind field can be better understood by using similar methods with wider bandwidth signals, such as the GPS L5 or Galileo E5 signals. For this research purpose, a prototype data collection system was developed to handle the necessary data sampling speeds for the L5 and E5 signals. This system used a Universal Software Radio Peripheral X300 device configured to sample at 100 MHz. A receiver was designed to generate DDMs with the L5 signal through zero-padded FFT techniques for cross-correlations. Lab tests showed that the resulting DDMs have the proper sinc function behavior with respect to doppler frequency and triangle function behavior to time delay. For future field experiments, data will be obtained by mounting the prototype system to the National Oceanic and Atmospheric Administration (NOAA) Hurricane Hunter aircraft during the 2017 hurricane season, and wind speed retrieval will be performed by analyzing the DDMs generated by the receiver
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