26,712 research outputs found

    Technology transfer and cultural exchange: Western scientists and engineers encounter late Tokugawa and Meiji Japan

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    [FIRST PARAGRAPH] During the last decade of the nineteenth century, the Engineer was only one of many British and American publications that took an avid interest in the rapid rise of Japan to the status of a fully industrialized imperial power on a par with major European nations. In December 1897 this journal published a photographic montage of "Pioneers of Modem Engineering Education in Japan" (Figure I), showing a selection of the Japanese and Western teachers who had worked to bring about this singular transformation.' The predominance of Japanese figures in this representation is highly significant: it is an acknowledgment by British observers that the industrialization of Japan-the "Britain of the East"-was not a feat accomplished solely by Western experts who transferred their science and technology to passive Japanese recipients. Yet in focusing primarily on native teachers active in Japan after 1880, this image excludes several of the very foreigners who had trained this indigenous workforce in the preceding decade. Rather than attempting to assess the careers of each of the many international experts involved in Western encounters with Japan before and after the Meiji restoration in 1868, we will focus on disaggregating the highly individualized responses of just some of the Englishspeaking characters. In documenting their diverse encounters with Japanese people and technologies, we will look at the complex phenomena of cultural exchange in which they participated, not always without chauvinism or resistance

    Active Markov Information-Theoretic Path Planning for Robotic Environmental Sensing

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    Recent research in multi-robot exploration and mapping has focused on sampling environmental fields, which are typically modeled using the Gaussian process (GP). Existing information-theoretic exploration strategies for learning GP-based environmental field maps adopt the non-Markovian problem structure and consequently scale poorly with the length of history of observations. Hence, it becomes computationally impractical to use these strategies for in situ, real-time active sampling. To ease this computational burden, this paper presents a Markov-based approach to efficient information-theoretic path planning for active sampling of GP-based fields. We analyze the time complexity of solving the Markov-based path planning problem, and demonstrate analytically that it scales better than that of deriving the non-Markovian strategies with increasing length of planning horizon. For a class of exploration tasks called the transect sampling task, we provide theoretical guarantees on the active sampling performance of our Markov-based policy, from which ideal environmental field conditions and sampling task settings can be established to limit its performance degradation due to violation of the Markov assumption. Empirical evaluation on real-world temperature and plankton density field data shows that our Markov-based policy can generally achieve active sampling performance comparable to that of the widely-used non-Markovian greedy policies under less favorable realistic field conditions and task settings while enjoying significant computational gain over them.Comment: 10th International Conference on Autonomous Agents and Multiagent Systems (AAMAS 2011), Extended version with proofs, 11 page

    When CoGeNT met PAMELA

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    If the excess events from the CoGeNT experiment arise from elastic scatterings of a light dark matter off the nuclei, crossing symmetry implies non-vanishing annihilation cross-sections of the light dark matter into hadronic final states inside the galactic halo, which we confront with the anti-proton spectrum measured by the PAMELA collaboration. We consider two types of effective interactions between the dark matter and the quarks: 1) contact interactions from integrating out heavy particles and 2) long-range interactions due to the electromagnetic properties of the dark matter. The lack of excess in the anti-proton spectrum results in tensions for a scalar and, to a less extent, a vector dark matter interacting with the quarks through the Higgs portal.Comment: 15 pages, 3 figures. Updated references and included effects of solar modulatio

    Elementary Particles of Conventional Field Theory as Regge Poles. IV

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    The usual field theory of spin 0 "nucleons" coupled to vector mesons (or heavy photons) is studied in order to find out whether the nucleon lies on a Regge trajectory. Photon-nucleon scattering is examined, to each order in the coupling constant, with the highest power of ln cosθ retained. It is found that a suitable Regge trajectory is generated, but that the nucleon does not lie on it. The nucleon pole term in the scattering amplitude corresponds to a fixed singularity in angular momentum. The spin 0 "nucleon" thus behaves differently from a particle of spin ½

    Reciprocal relativity of noninertial frames and the quaplectic group

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    Newtonian mechanics has the concept of an absolute inertial rest frame. Special relativity eliminates the absolute rest frame but continues to require the absolute inertial frame. General relativity solves this for gravity by requiring particles to have locally inertial frames on a curved position-time manifold. The problem of the absolute inertial frame for other forces remains. We look again at the transformations of frames on an extended phase space with position, time, energy and momentum degrees of freedom. Under nonrelativistic assumptions, there is an invariant symplectic metric and a line element dt^2. Under special relativistic assumptions the symplectic metric continues to be invariant but the line elements are now -dt^2+dq^2/c^2 and dp^2-de^2/c^2. Max Born conjectured that the line element should be generalized to the pseudo- orthogonal metric -dt^2+dq^2/c^2+ (1/b^2)(dp^2-de^2/c^2). The group leaving these two metrics invariant is the pseudo-unitary group of transformations between noninertial frames. We show that these transformations eliminate the need for an absolute inertial frame by making forces relative and bounded by b and so embodies a relativity that is 'reciprocal' in the sense of Born. The inhomogeneous version of this group is naturally the semidirect product of the pseudo-unitary group with the nonabelian Heisenberg group. This is the quaplectic group. The Heisenberg group itself is the semidirect product of two translation groups. This provides the noncommutative properties of position and momentum and also time and energy that are required for the quantum mechanics that results from considering the unitary representations of the quaplectic group.Comment: Substantial revision, Publicon LaTe

    The Influence of Metallicity on Star Formation in Protogalaxies

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    In cold dark matter cosmological models, the first stars to form are believed to do so within small protogalaxies. We wish to understand how the evolution of these early protogalaxies changes once the gas forming them has been enriched with small quantities of heavy elements, which are produced and dispersed into the intergalactic medium by the first supernovae. Our initial conditions represent protogalaxies forming within a fossil H II region, a previously ionized region that has not yet had time to cool and recombine. We study the influence of low levels of metal enrichment on the cooling and collapse of ionized gas in small protogalactic halos using three-dimensional, smoothed particle hydrodynamics (SPH) simulations that incorporate the effects of the appropriate chemical and thermal processes. Our previous simulations demonstrated that for metallicities Z < 0.001 Z_sun, metal line cooling alters the density and temperature evolution of the gas by less than 1% compared to the metal-free case at densities below 1 cm-3) and temperatures above 2000 K. Here, we present the results of high-resolution simulations using particle splitting to improve resolution in regions of interest. These simulations allow us to address the question of whether there is a critical metallicity above which fine structure cooling from metals allows efficient fragmentation to occur, producing an initial mass function (IMF) resembling the local Salpeter IMF, rather than only high-mass stars.Comment: 3 pages, 2 figures, First Stars III conference proceeding
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