28,171 research outputs found

    Tool for installing or extracting small bulbs in limited-access spaces

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    Installing and extracting component of tool is plastic tubing with inside diameter which provides snug fit over bulb. Other components, which provide sturdiness and ease of operation, consist of metal tube, with collar near one end, and plunger, with knob on one end and Teflon tip on the other

    Feasibility study of aileron and spoiler control systems for large horizontal axis wind turbines

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    The feasibility of using aileron or spoiler controls as alternates to pitch control for large horizontal axis wind turbines was studied. The NASA Mod-0 100 kw machine was used as the basis for the study. Specific performance studies were conducted for 20% chord ailerons over the outboard 30% span, and for 10% chord spoilers over the same portion of the span. Both control systems utilized control deflections up to 60 deg. Results of the study show that either ailerons or spoilers can provide the control necessary to limit turbine power in high wind conditions. The aileron system, as designed, provides overspeed protection at hurricane wind speeds, low wind speed starting torque of 778 N-m (574 ft. lb) at 3.6 m/sec, and a 1.3 to 1.5% increase in annual energy compared to a fixed pitch rotor. The aileron control system preliminary design study includes aileron loads analysis and the design of a failsafe flyweight actuator for overspeed protection in the event of a hydraulic system failure

    Approaches to Faith, Guest Editorial Preface

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    Springer. We find in contemporary culture starkly contrasting estimates of the value of faith. On the one hand, for many people, faith is a virtue or positive human value, something associated with understanding, hope, and love, something to be inculcated, maintained, and cherished. On the other hand, for many people, faith is a vice, something associated with dogmatism, arrogance, and close-mindedness, something to be avoided at all costs. The papers included in this special (double) issue on approaches to faith explore questions about faith in a variety of settings through a diverse range of examples, both secular and religious. The attempt to deepen our understanding of faith in the context of ordinary human relationships (e.g., between parents and children, friends, generals and their armies, business partners, citizens and the state), a commitment to ideals, or the pursuit of significant goals is clearly of general philosophical interest, as is the examination of potential connections between faith and topics such as trust or reliance

    Nanoscale alpha-structural domains in the phonon-glass thermoelectric material beta-Zn4Sb3

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    A study of the local atomic structure of the promising thermoelectric material beta-Zn4Sb3, using atomic pair distribution function (PDF) analysis of x-ray- and neutron-diffraction data, suggests that the material is nanostructured. The local structure of the beta phase closely resembles that of the low-temperature alpha phase. The alpha structure contains ordered zinc interstitial atoms which are not long range ordered in the beta phase. A rough estimate of the domain size from a visual inspection of the PDF is <~10 nm. It is probable that the nanoscale domains found in this study play an important role in the exceptionally low thermal conductivity of beta-Zn4Sb3

    The Relativistic Particle: Dirac observables and Feynman propagator

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    We analyze the algebra of Dirac observables of the relativistic particle in four space-time dimensions. We show that the position observables become non-commutative and the commutation relations lead to a structure very similar to the non-commutative geometry of Deformed Special Relativity (DSR). In this framework, it appears natural to consider the 4d relativistic particle as a five dimensional massless particle. We study its quantization in terms of wave functions on the 5d light cone. We introduce the corresponding five-dimensional action principle and analyze how it reproduces the physics of the 4d relativistic particle. The formalism is naturally subject to divergences and we show that DSR arises as a natural regularization: the 5d light cone is regularized as the de Sitter space. We interpret the fifth coordinate as the particle's proper time while the fifth moment can be understood as the mass. Finally, we show how to formulate the Feynman propagator and the Feynman amplitudes of quantum field theory in this context in terms of Dirac observables. This provides new insights for the construction of observables and scattering amplitudes in DSR.Comment: 14 pages, Revtex

    A Scalable Asynchronous Distributed Algorithm for Topic Modeling

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    Learning meaningful topic models with massive document collections which contain millions of documents and billions of tokens is challenging because of two reasons: First, one needs to deal with a large number of topics (typically in the order of thousands). Second, one needs a scalable and efficient way of distributing the computation across multiple machines. In this paper we present a novel algorithm F+Nomad LDA which simultaneously tackles both these problems. In order to handle large number of topics we use an appropriately modified Fenwick tree. This data structure allows us to sample from a multinomial distribution over TT items in O(logT)O(\log T) time. Moreover, when topic counts change the data structure can be updated in O(logT)O(\log T) time. In order to distribute the computation across multiple processor we present a novel asynchronous framework inspired by the Nomad algorithm of \cite{YunYuHsietal13}. We show that F+Nomad LDA significantly outperform state-of-the-art on massive problems which involve millions of documents, billions of words, and thousands of topics

    Sine-Gordon Soliton on a Cnoidal Wave Background

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    The method of Darboux transformation, which is applied on cnoidal wave solutions of the sine-Gordon equation, gives solitons moving on a cnoidal wave background. Interesting characteristics of the solution, i.e., the velocity of solitons and the shift of crests of cnoidal waves along a soliton, are calculated. Solutions are classified into three types (Type-1A, Type-1B, Type-2) according to their apparent distinct properties.Comment: 11 pages, 5 figures, Contents change

    Sub-shot-noise photon-number correlation in mesoscopic twin-beam of light

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    We demonstrate sub-shot-noise photon-number correlations in a (temporal) multimode mesoscopic (103\sim 10^3 detected photons) twin-beam produced by ps-pulsed spontaneous non-degenerate parametric downconversion. We have separately detected the signal and idler distributions of photons collected in twin coherence areas and found that the variance of the photon-count difference goes below the shot-noise limit by 3.25 dB. The number of temporal modes contained in the twin-beam, as well as the size of the twin coherence areas, depends on the pump intensity. Our scheme is based on spontaneous downconversion and thus does not suffer from limitations due to the finite gain of the parametric process. Twin-beams are also used to demonstrate the conditional preparation of a nonclassical (sub-Poissonian) state.Comment: 5 pages, 5 (low-res) figures, to appear on PR
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