3,014 research outputs found

    Learning to Discriminate Information for Online Action Detection

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    From a streaming video, online action detection aims to identify actions in the present. For this task, previous methods use recurrent networks to model the temporal sequence of current action frames. However, these methods overlook the fact that an input image sequence includes background and irrelevant actions as well as the action of interest. For online action detection, in this paper, we propose a novel recurrent unit to explicitly discriminate the information relevant to an ongoing action from others. Our unit, named Information Discrimination Unit (IDU), decides whether to accumulate input information based on its relevance to the current action. This enables our recurrent network with IDU to learn a more discriminative representation for identifying ongoing actions. In experiments on two benchmark datasets, TVSeries and THUMOS-14, the proposed method outperforms state-of-the-art methods by a significant margin. Moreover, we demonstrate the effectiveness of our recurrent unit by conducting comprehensive ablation studies

    Letter to F.D. Moon from A. Mitchell Salone regarding information about and photos of the Colored School in Wewoka

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    Letter to F.D. Moon regarding a book being written on African American schools. The author asks for photos of the school and shows appreciation for how he runs the school

    We Reach the Moon. Title page inscribed by the author.

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    On 20 July 1969, Neil Armstrong and Buzz Aldrin became the first humans to land on the moon. The achievement inspired a host of products and memorabilia. On display from the publishing collection of Seymour Lawrence is both the German and American editions of the children’s 1969 picture book Journey to the Moon by artist Erich Fuchs who depicts the eight-day voyage with cubist modernism. The author of We Reach the Moon was the New York Times science reporter, and he inscribed his paperback to Mississippi writer Willie Morris and family.https://egrove.olemiss.edu/space_exhibit_2020/1012/thumbnail.jp

    On lunar collision orbits: New methodologies for Moon-to-Moon transfer design

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    Many interplanetary missions massively leverage the lunar gravitational pull in the so-called low-energy regime to converge to their aim, saving consistent amount of fuel. Among these, two future Japanese spacecraft are expected to repeatedly encounter the Moon along their trajectories to either facilitate the escape from the Earth–Moon system or opportunely target a specific region in its neighbourhood. Although never actively employed for preliminary trajectory design, lunar collision orbits have shown a rich dynamical structure and an applicability for both medium- and low-energy regimes. These characteristics, together with their intrinsic nature of being close to trajectories experiencing lunar fly-by, have encouraged this research. In this work, lunar collision orbits are employed to delineate a method for obtaining ballistic transfers between two successive lunar encounters, briefly addressed as Moon-to-Moon. This study is first carried out with the assumptions of the autonomous Circular Restricted Three-Body Problem, subsequently extended to the nonautonomous Bi-circular Restricted Four-Body Problem, including the solar gravitational influence.Poincaré cuts are extensively used as a dimensionality reductant for lunar collision orbits: this allows to ascertain their similar behaviour with trajectories flybying the Moon, whose characteristics are partly foreseen by determining the associated intersection with the same cut. A patching is performed at the cut to obtain both single and multiple ballistic Moon-to-Moon transfers. The strict bond of lunar collision orbits with the invariant manifolds of simple periodic orbits about Lagrangian points is confirmed and exploited to design ballistic itineraries connecting highly elliptic orbits about the Earth to horizontal Lyapunov orbits of the Earth–Moon system, via a single Moon-to-Moon transfer. With the usage of the lunar collision orbits and the Poincaré cut, a simple optimization technique is implemented to retrieve a properly defined Moon-to-Moon transfer from a trajectory missing a second fly-by with the Moon. Including the presence of the Sun, a similar method for obtaining single and multiple Moon-to-Moon transfers is developed. A classification of lunar double-collision transfers is then performed within the same framework, highlighting their similarity with other studies in past literature, eventually leading to the construction of a database of Moon-to-Moon transfers. The latter, conceived as an improvement with respect to the former version by adding the lunar gravitational influence, shows its applicability in real preliminary trajectory design.Aerospace Engineerin

    Moon Dog [Translation]

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    A Japanese to English translation of the poem Moon Dog originally written by Mizuho Ishid

    New solar-sail orbits for polar observation of the earth and moon

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    In this paper, a new family of solar-sail periodic orbits with adequate properties for polar observation of the Earth and moon is developed under the simplified but nonautonomous dynamics of the solar-sail augmented Earth–moon circular restricted three-body problem. The novel orbits, termed “distant-circular orbits,” are found through differential correction and continuation and employ a simple sun-facing steering law for the solar sail. A basic coverage analysis shows that one of the distant-circular orbits is capable of providing continuous coverage of both the Earth’s and lunar north (or south) poles with just a single sailcraft at a minimum elevation angle of 14 deg and an average range of six Earth–moon distances. Moreover, simple transfer trajectories between orbits of the family are found, so that the sailcraft can switch between observing the northern and southern latitudes of the Earth and moon during a single mission. Subsequently, using multiple-shooting differential correction, all results are migrated to a higher-fidelity dynamic framework that considers, among others, the eccentricity of the moon’s orbit. The perturbations cause the periodicity of the orbits to break, turning them into seemingly quasi-periodic orbits, but it is shown that the coverage capabilities are maintained. Finally, an active control strategy is developed to counteract part of the perturbing effects such that, by appropriately steering the sail, the apparent quasi-periodicity of the orbits is enhanced and the deviation from the unperturbed orbits is reduced.Accepted Author ManuscriptAstrodynamics & Space Mission

    Half Moon Lake School District No. 2785

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    Photograph - Students, likely at Half Moon Lake School, near Waugh, Alberta. Teacher is P. Kowalski. ATS 4-59-23-W

    Effects of Message Framing, Product Type, and Temporal Distance on Consumer Attitude

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    System design of LUMIO: A CubeSat at Earth-Moon L2 for observing lunar meteoroid impacts

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    The Earth–Moon system is constantly being bombarded by a significant number of meteoroids with different sizes and velocities. Observation of the lunar surface impacts will enable characterization of the lunar meteoroid flux, which is similar to that of the Earth, and provide more detailed information on meteoroid size, velocity, temporal and spatial distribution. The Lunar Meteoroid Impacts Observer (LUMIO) is a CubeSat mission at Earth–Moon L2 to observe, quantify, and characterise these meteoroid impacts by detecting their flashes on the lunar farside. LUMIO is one of the two winners of ESA’s LUCE (Lunar CubeSat for Exploration) SysNova competition, and as such is being considered by ESA for implementation in the near future. This paper will present the design of the LUMIO spacecraft that will host the payload to capture the meteoroid flashes. Key system specifications, trade-offs and consequent design iterations are presented. The final design yields a feasible spacecraft budget and a configuration that enables the LUMIO mission to be realized by 2023.The spacecraft is a 12U form-factor CubeSat, with a mass of less than 22 kg. A zero-redundancy and COTS based approach has been adopted for the spacecraft design. A strong emphasis has been placed on realizing high onboard autonomy. A novel and autonomous navigation strategy that uses optical observations of the Earth and the Moon is proposed for navigation around the Moon and beyond. The payload and navigation are the key drivers of the pointing requirements. Pointing requirements are achieved through reaction wheels, IMUs, star trackers, and fine sun sensors. A hybrid micro-propulsion system is included for orbital control, de-tumbling, and reaction wheel desaturation. Steady solar power availability is ensured with a one-axis solar array drive assembly in combination with an innovative attitude algorithm. Communication with Earth is through the Lunar Orbiter with a low-bandwidth UHF link, which places high constraints on the data throughput. An onboard payload data processor has been designed that compresses the science data to a fraction of the raw data with no loss of information.The paper will conclude with the key findings of a concurrent design review of the LUMIO spacecraft design that was performed at ESA/ESTEC’s Concurrent Design Facility (CDF). The major design changes are outlined along with a summary and discussion of the iterated design.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Space Systems EgineeringAstrodynamics & Space Mission
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