21,623 research outputs found

    Workshop on an Assessment of Gas-Side Fouling in Fossil Fuel Exhaust Environments

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    The state of the art of gas side fouling in fossil fuel exhaust environments was assessed. Heat recovery applications were emphasized. The deleterious effects of gas side fouling including increased energy consumption, increased material losses, and loss of production were identified

    Approximation solvability of nonlinear equations

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    NONLINEAR NON-LOCAL BOUNDARY-VALUE PROBLEMS AND PERTURBED HAMMERSTEIN INTEGRAL EQUATIONS

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    AbstractMotivated by some non-local boundary-value problems (BVPs) that arise in heat-flow problems, we establish new results for the existence of non-zero solutions of integral equations of the formu(t)=γ(t)α[u]+Gk(t,s)f(s,u(s))ds, u(t)=\gamma(t)\alpha[u]+\int_{G}k(t,s)f(s,u(s))\,\mathrm{d}s, where GG is a compact set in Rn\mathbb{R}^{n}. Here α[u]\alpha[u] is a positive functional and ff is positive, while kk and γ\gamma may change sign, so positive solutions need not exist. We prove the existence of multiple non-zero solutions of the BVPs under suitable conditions. We show that solutions of the BVPs lose positivity as a parameter decreases. For a certain parameter range not all solutions can be positive, but for one of the boundary conditions we consider we show that there are positive solutions for certain types of nonlinearity. We also prove a uniqueness result

    Generation and measurement of nonstationary random processes technical note no. 3

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    Generation and measurement of nonstationary stochastic processes related to Monte Carlo studies with analog compute

    Humpback and Fin Whaling in the Gulf of Maine from 1800 to 1918

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    The history of whaling in the Gulf of Maine was reviewed primarily to estimate removals of humpback whales, Megaptera novaeangliae, especially during the 19th century. In the decades from 1800 to 1860, whaling effort consisted of a few localized, small-scale, shore-based enterprises on the coast of Maine and Cape Cod, Mass. Provincetown and Nantucket schooners occasionally conducted short cruises for humpback whales in New England waters. With the development of bomb-lance technology at mid century, the ease of killing humpback whales and fin whales, Balaenoptera physalus, increased. As a result, by the 1870’s there was considerable local interest in hunting rorquals (baleen whales in the family Balaenopteridae, which include the humpback and fin whales) in the Gulf of Maine. A few schooners were specially outfitted to take rorquals in the late 1870’s and 1880’s although their combined annual take was probably no more than a few tens of whales. Also in about 1880, fishing steamers began to be used to hunt whales in the Gulf of Maine. This steamer fishery grew to include about five vessels regularly engaged in whaling by the mid 1880’s but dwindled to only one vessel by the end of the decade. Fin whales constituted at least half of the catch, which exceeded 100 animals in some years. In the late 1880’s and thereafter, few whales were taken by whaling vessels in the Gulf of Maine

    Boxfishes (Teleostei: Ostraciidae) as a model system for fishes swimming with many fins: kinematics

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    Swimming movements in boxfishes were much more complex and varied than classical descriptions indicated. At low to moderate rectilinear swimming speeds (<5 TL s^(-1), where TL is total body length), they were entirely median- and paired-fin swimmers, apparently using their caudal fins for steering. The pectoral and median paired fins generate both the thrust needed for forward motion and the continuously varied, interacting forces required for the maintenance of rectilinearity. It was only at higher swimming speeds (above 5 TL s^(-1)), when burst-and-coast swimming was used, that they became primarily body and caudal-fin swimmers. Despite their unwieldy appearance and often asynchronous fin beats, boxfish swam in a stable manner. Swimming boxfish used three gaits. Fin-beat asymmetry and a relatively nonlinear swimming trajectory characterized the first gait (0–1 TL s^(-1)). The beginning of the second gait (1–3 TL s^(-1)) was characterized by varying fin-beat frequencies and amplitudes as well as synchrony in pectoral fin motions. The remainder of the second gait (3–5 TL s^(-1)) was characterized by constant fin-beat amplitudes, varying finbeat frequencies and increasing pectoral fin-beat asynchrony. The third gait (>5 TL s^(-1)) was characterized by the use of a caudal burst-and-coast variant. Adduction was always faster than abduction in the pectoral fins. There were no measurable refractory periods between successive phases of the fin movement cycles. Dorsal and anal fin movements were synchronized at speeds greater than 2.5 TL s^(-1), but were often out of phase with pectoral fin movements

    Microwave-Induced Dephasing in One-Dimensional Metal Wires

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    We report on the effect of monochromatic microwave (MW) radiation on the weak localization corrections to the conductivity of quasi-one-dimensional (1D) silver wires. Due to the improved electron cooling in the wires, the MW-induced dephasing was observed without a concomitant overheating of electrons over wide ranges of the MW power PMWP_{MW} and frequency ff. The observed dependences of the conductivity and MW-induced dephasing rate on PMWP_{MW} and ff are in agreement with the theory by Altshuler, Aronov, and Khmelnitsky \cite{Alt81}. Our results suggest that in the low-temperature experiments with 1D wires, saturation of the temperature dependence of the dephasing time can be caused by an MW electromagnetic noise with a sub-pW power.Comment: 4 pages with 4 figures, paper revised, accepted by Phys Rev Let

    Universal saturation of electron dephasing in three-dimensional disordered metals

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    We have systematically investigated the low-temperature electron dephasing times τϕ\tau_\phi in more than 40 three-dimensional polycrystalline impure metals with distinct material characteristics. In all cases, a saturation of the dephasing time is observed below about a (few) degree(s) Kelvin, depending on samples. The value of the saturated dephasing time τ0\tau_0 [τϕ(T0K)\equiv \tau_\phi (T \to 0 {\rm K})] falls basically in the range 0.005 to 0.5 ns for all samples. Particularly, we find that τ0\tau_0 scales with the electron diffusion constant DD as τ0Dα\tau_0 \sim D^{- \alpha}, with α\alpha close to or slightly larger than 1, for over two decades of DD from about 0.1 to 10 cm2^2/s. Our observation suggests that the saturation behavior of τϕ\tau_\phi is universal and intrinsic in three-dimensional polycrystalline impure metals. A complete theoretical explanation is not yet available.Comment: 4 pages, 3 eps figure

    ‘Living on the edge’: using cognitive filters to appraise experience of environmental risk

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    Individuals respond to an experience of risk, both in attitudinal and behavioural terms as a result of how that experience is interpreted and appraised. Experience of local flooding can in theory, inform individuals’ attitudes towards climate change. This trend however, is not observed in all cases and is highly dependent on the local, situational context. This paper postulates that the variation observed in attitudinal and behavioural responses by farmers to climate change following experiences of local flooding can, in part, be explained by the Cognitive Filters of Experience Appraisal Model introduced in this paper. The model is developed firstly through a review of the existing literature concerning appraisal (cognitive and experience). Secondly, the model is framed by empirical research via fifteen face to face interviews with farmers in Gloucestershire, England, who have all directly experienced flooding in recent years. The study is exploratory in nature, and the qualitative data serve as contextualised accounts of the different patterns of experience appraisal. The paper contributes to existing literature by developing current understandings of experience appraisal as well as providing qualitative detail to an area which has generally only been researched quantitatively. The model of experience appraisal which is put forward could be applied to multiple contexts of environmental risk
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