5,449 research outputs found

    Aircraft/island/ship/satellite intercomparison: Preliminary results from July 16, 1987

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    The First ISCCP Regional Experiment (FIRE) objective of validating and improving satellite algorithms for inferring cloud properties from satellite radiances was one of the central motivating factors in the design of the specific field experimental strategies used in the July, 1987 marine stratocumulus intensive field observations (IFO). The in situ measuring platforms were deployed to take maximum advantage of redundant measurements (for intercomparison of the in situ sensors) and to provide optimal coverage within satellite images. One of the most ambitious of these strategies was the attempt to coordinate measurements from San Nicolas Island (SNI), the R/V Pt. Sur, the meteorological aircraft, and the satellites. For the most part, this attempt was frustrated by flight restrictions in the vicinity of SNI. The exception was the mission of July 16, 1987, which achieved remarkable success in the coordination of the platforms. This presentation concerns operations conducted by the National Center for Atmospheric Research (NCAR) Electra and how data from the Electra can be integrated with and compared to data from the Pt. Sur, SNI, and the satellites. The focus is on the large-scale, integrated picture of the conditions on July 16 from the perspective of the Electra's flight operations

    Army Professionalism, the Military Ethic, and Officership in the 21st Century

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    The authors address what they—and many others—perceived to be a decline in military professionalism in the Army officer corps. The authors first describe the ethical, technical, and political components of military professionalism and then address the causes for the decline. They conclude by proposing a set of principles which, if adhered to, will reinvigorate the vision of the officer corps and motivate the corps to selfless service.https://press.armywarcollege.edu/monographs/1145/thumbnail.jp

    Reservoir Computing Approach to Robust Computation using Unreliable Nanoscale Networks

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    As we approach the physical limits of CMOS technology, advances in materials science and nanotechnology are making available a variety of unconventional computing substrates that can potentially replace top-down-designed silicon-based computing devices. Inherent stochasticity in the fabrication process and nanometer scale of these substrates inevitably lead to design variations, defects, faults, and noise in the resulting devices. A key challenge is how to harness such devices to perform robust computation. We propose reservoir computing as a solution. In reservoir computing, computation takes place by translating the dynamics of an excited medium, called a reservoir, into a desired output. This approach eliminates the need for external control and redundancy, and the programming is done using a closed-form regression problem on the output, which also allows concurrent programming using a single device. Using a theoretical model, we show that both regular and irregular reservoirs are intrinsically robust to structural noise as they perform computation

    Optical and Infrared Photometry of the Unusual Type Ia Supernova 2000cx

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    We present optical and infrared photometry of the unusual Type Ia supernova 2000cx. With the data of Li et al. (2001) and Jha (2002), this comprises the largest dataset ever assembled for a Type Ia SN, more than 600 points in UBVRIJHK. We confirm the finding of Li et al. regarding the unusually blue B-V colors as SN 2000cx entered the nebular phase. Its I-band secondary hump was extremely weak given its B-band decline rate. The V minus near infrared colors likewise do not match loci based on other slowly declining Type Ia SNe, though V-K is the least ``abnormal''. In several ways SN 2000cx resembles other slow decliners, given its B-band decline rate (Delta m_15(B) = 0.93), the appearance of Fe III lines and weakness of Si II in its pre-maximum spectrum, the V-K colors and post-maximum V-H colors. If the distance modulus derived from Surface Brightness Fluctuations of the host galaxy is correct, we find that the rate of light increase prior to maximum, the characteristics of the bolometric light curve, and the implied absolute magnitude at maximum are all consistent with a sub-luminous object with Delta m_15(B) ~ 1.6-1.7 having a higher than normal kinetic energy.Comment: 46 pages, 17 figures, to be published in Publications of the Astronomical Society of the Pacifi

    Distinguishing artefacts:evaluating the saturation point of convolutional neural networks

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    Prior work has shown Convolutional Neural Networks (CNNs) trained on surrogate Computer Aided Design (CAD) models are able to detect and classify real-world artefacts from photographs. The applications of which support twinning of digital and physical assets in design, including rapid extraction of part geometry from model repositories, information search \& retrieval and identifying components in the field for maintenance, repair, and recording. The performance of CNNs in classification tasks have been shown dependent on training data set size and number of classes. Where prior works have used relatively small surrogate model data sets (<100<100 models), the question remains as to the ability of a CNN to differentiate between models in increasingly large model repositories. This paper presents a method for generating synthetic image data sets from online CAD model repositories, and further investigates the capacity of an off-the-shelf CNN architecture trained on synthetic data to classify models as class size increases. 1,000 CAD models were curated and processed to generate large scale surrogate data sets, featuring model coverage at steps of 10^{\circ}, 30^{\circ}, 60^{\circ}, and 120^{\circ} degrees. The findings demonstrate the capability of computer vision algorithms to classify artefacts in model repositories of up to 200, beyond this point the CNN's performance is observed to deteriorate significantly, limiting its present ability for automated twinning of physical to digital artefacts. Although, a match is more often found in the top-5 results showing potential for information search and retrieval on large repositories of surrogate models.Comment: 6 Pages, 5 Figures, 2 Tables, Conference, Design Engineering, CNN, Digital Twi

    Comparison of OLYMPUS beacon and radiometric attenuation measurements at Blacksburg, Virginia

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    Measurements of attenuation of the 20 and 30 GHz beacons onboard the OLYMPUS satellite are compared to simultaneous observations of atmospheric attenuation by a multichannel microwave radiometer along the same path. Departures from high correlation between the two measurements are believed to be related to differences in antenna beamwidths. Mean equivalent zenith attenuations derived from the slant path data are compared to zenith observations made at previous locations

    Defect detection in nano-scale transistors based on radio-frequency reflectometry

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    Radio-frequency reflectometry in silicon single-electron transistors (SETs) is presented. At low temperatures (<4 K), in addition to the expected Coulomb blockade features associated with charging of the SET dot, quasi-periodic oscillations are observed that persist in the fully depleted regime where the SET dot is completely empty. A model, confirmed by simulations, indicates that these oscillations originate from charging of an unintended floating gate located in the heavily doped polycrystalline silicon gate stack. The technique used in this experiment can be applied for detailed spectroscopy of various charge defects in nanoscale SETs and field effect transistorsComment: 3 pages, 3 figure

    In Situ Resistance Measurements of Strained Carbon Nanotubes

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    We investigate the response of multi-walled carbon nanotubes to mechanical strain applied with an Atomic Force Microscope (AFM) probe. We find that in some samples, changes in the contact resistance dominate the measured resistance change. In others, strain large enough to fracture the tube can be applied without a significant change in the contact resistance. In this case we observe that enough force is applied to break the tube without any change in resistance until the tube fails. We have also manipulated the ends of the broken tube back in contact with each other, re-establishing a finite resistance. We observe that in this broken configuration the resistance of the sample is tunable to values 15-350 kW greater than prior to breaking.Comment: Submitted to Applied Physics Letter

    Remote sensing data from CLARET: A prototype CART data set

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    The data set containing radiation, meteorological , and cloud sensor observations is documented. It was prepared for use by the Department of Energy's Atmospheric Radiation Measurement (ARM) Program and other interested scientists. These data are a precursor of the types of data that ARM Cloud And Radiation Testbed (CART) sites will provide. The data are from the Cloud Lidar And Radar Exploratory Test (CLARET) conducted by the Wave Propagation Laboratory during autumn 1989 in the Denver-Boulder area of Colorado primarily for the purpose of developing new cloud-sensing techniques on cirrus. After becoming aware of the experiment, ARM scientists requested archival of subsets of the data to assist in the developing ARM program. Five CLARET cases were selected: two with cirrus, one with stratus, one with mixed-phase clouds, and one with clear skies. Satellite data from the stratus case and one cirrus case were analyzed for statistics on cloud cover and top height. The main body of the selected data are available on diskette from the Wave Propagation Laboratory or Los Alamos National Laboratory
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