189,758 research outputs found

    Investigation of split injection in a single cylinder optical diesel engine

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    SAE paper 2010-01-0605, Copyright © 2010 SAE International. This paper is posted on this site with permission from SAE International, and is for viewing only. Further use and distribution of this paper is not permitted without permission from SAE.Over the last decade, the diesel engine has made dramatic progress in its performance and market penetration. However, in order to meet future emissions legislations, Nitrogen Oxides (NOx) and particulate matters’ (PM) emissions will need to be reduced simultaneously. Nowadays researchers are focused on different combustion modes which can have a great potential for both low soot and low NOx. In order to achieve this, different injection strategies have been investigated. This study investigates the effects of split injection strategies with high levels of Exhaust Gas Recirculation (EGR) on combustion performance and emissions in a single cylinder direct injection optical diesel engine. The investigation is focused on the effects of injection timing of split injection strategies. A Ricardo Hydra single cylinder optical engine was used in which conventional experimental methods like cylinder pressure data, heat release analysis and exhaust emissions analysis were applied. Optical techniques like direct spray and combustion visualization were applied by means of a high speed imaging system with a copper vapor laser illumination system and a high-speed two-color system was applied to obtain in-cylinder diesel combustion temperature and soot measurements distributions

    Nonequilibrium spin-transfer torque in SFNFS junctions

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    We report theoretical results for the nonequilibrium spin current and spin-transfer torque in voltage-biased SFNFS Josephson structures. The subharmonic gap structures and high voltage asymptotic behaviors of the dc and ac components of the spin current are analyzed and related to the spin-dependent inelastic scattering of quasiparticles at both F layers.Comment: minor changes, published versio

    Evidence for very strong electron-phonon coupling in YBa_{2}Cu_{3}O_{6}

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    From the observed oxygen-isotope shift of the mid-infrared two-magnon absorption peak of YBa2_{2}Cu3_{3}O6_{6}, we evaluate the oxygen-isotope effect on the in-plane antiferromagnetic exchange energy JJ. The exchange energy JJ in YBa2_{2}Cu3_{3}O6_{6} is found to decrease by about 0.9% upon replacing 16^{16}O by 18^{18}O, which is slightly larger than that (0.6%) in La2_{2}CuO4_{4}. From the oxygen-isotope effects, we determine the lower limit of the polaron binding energy, which is about 1.7 eV for YBa2_{2}Cu3_{3}O6_{6} and 1.5 eV for La2_{2}CuO4_{4}, in quantitative agreement with angle-resolved photoemission data, optical conductivity data, and the parameter-free theoretical estimate. The large polaron binding energies in the insulating parent compounds suggest that electron-phonon coupling should also be strong in doped superconducting cuprates and may play an essential role in high-temperature superconductivity.Comment: 4 pages, 1 figur

    A Generalization of Mathieu Subspaces to Modules of Associative Algebras

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    We first propose a generalization of the notion of Mathieu subspaces of associative algebras A\mathcal A, which was introduced recently in [Z4] and [Z6], to A\mathcal A-modules M\mathcal M. The newly introduced notion in a certain sense also generalizes the notion of submodules. Related with this new notion, we also introduce the sets σ(N)\sigma(N) and τ(N)\tau(N) of stable elements and quasi-stable elements, respectively, for all RR-subspaces NN of A\mathcal A-modules M\mathcal M, where RR is the base ring of A\mathcal A. We then prove some general properties of the sets σ(N)\sigma(N) and τ(N)\tau(N). Furthermore, examples from certain modules of the quasi-stable algebras [Z6], matrix algebras over fields and polynomial algebras are also studied.Comment: A new case has been added; some mistakes and misprints have been corrected. Latex, 31 page

    Relative FP-injective and FP-flat complexes and their model structures

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    In this paper, we introduce the notions of FPn{\rm FP}_n-injective and FPn{\rm FP}_n-flat complexes in terms of complexes of type FPn{\rm FP}_n. We show that some characterizations analogous to that of injective, FP-injective and flat complexes exist for FPn{\rm FP}_n-injective and FPn{\rm FP}_n-flat complexes. We also introduce and study FPn{\rm FP}_n-injective and FPn{\rm FP}_n-flat dimensions of modules and complexes, and give a relation between them in terms of Pontrjagin duality. The existence of pre-envelopes and covers in this setting is discussed, and we prove that any complex has an FPn{\rm FP}_n-flat cover and an FPn{\rm FP}_n-flat pre-envelope, and in the case n2n \geq 2 that any complex has an FPn{\rm FP}_n-injective cover and an FPn{\rm FP}_n-injective pre-envelope. Finally, we construct model structures on the category of complexes from the classes of modules with bounded FPn{\rm FP}_n-injective and FPn{\rm FP}_n-flat dimensions, and analyze several conditions under which it is possible to connect these model structures via Quillen functors and Quillen equivalences.Comment: 41 page

    Towards understanding the probability of 0+0^+ ground states in even-even many-body systems

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    For single-jj shells with j=7/2,9/2j={7/2}, {9/2} and 11/2, we relate the large probability of I+I^+ ground states to the largest (smallest) coefficients αI(vβ)J=<nvβI\alpha^J_{I(v \beta)} = <nv \beta I | AJAJnvβI>A^{J \dagger} \cdot A^J | n v\beta I>, where nn is the particle number, vv is the seniority, β\beta is an additional quantum number, and II is the angular momentum of the state. Interesting regularities of the probabilities of I+I^+ ground states are noticed and discussed for 4-particle systems. Several counter examples of the 0+0^+ ground state (0GS) predominance are noticed for the first time.Comment: 5 pages, 1 figure. Phys. Rev. C64, in pres
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