9,893 research outputs found
Investigation of split injection in a single cylinder optical diesel engine
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
An International Dynamic Term Structure Model with Economic Restrictions and Unspanned Risks
We construct a multi-country affine term structure model that contains unspanned macroeconomic and foreign exchange risks. The canonical version of the model is derived and is shown to be easy to estimate. We show that it is important to impose restrictions (including global asset pricing, carry trade fundamentals and maximal Sharpe ratios) on the prices of risk to obtain plausible decompositions of forward curves. The forecasts of interest rates and exchange rates from the restricted model match those from international survey data. Unspanned macroeconomic variables are important drivers of international term and foreign exchange risk premia as well as expected exchange rate changes.Asset Pricing; Exchange rates; Interest rates
The extinct tree fern Tempskya Corda from the Albian of Spain: Palaeophytogeographical and palaeoenvironmental implications
New evidence of the extinct tree fern of the genus Tempskya Corda from Albian deposits in western Eurasia (northeastern Spain) is presented. These plant fossil remains consist of several silicified false trunks measuring up to 1.20m long, some of which still preserve the apex. Rhizomes and petioles are more abundant in the apical zone of the false trunk. Some false trunks preserve charcoalified tissues that can be interpreted as evidence that palaeo-wildfires affected the false trunks several times from mostly the same direction. Sedimentological evidence suggests that the fern habitat was close to coastal, tidally influenced environments. These new fossils from the Albian of Spain fill the chronological and distributional gap of Tempskya that existed in Eurasia during the Early Cretaceous. Temporal and spatial changes in Tempskya distributions are proposed on several palaeogeographical maps
Atomic Interferometer with Amplitude Gratings of Light and its Applications to Atom Based Tests of the Equivalence Principle
We have developed a matter wave interferometer based on the diffraction of
atoms from effective absorption gratings of light. In a setup with cold
rubidium atoms in an atomic fountain the interferometer has been used to carry
out tests of the equivalence principle on an atomic basis. The gravitational
acceleration of the two isotopes 85Rb and 87Rb was compared, yielding a
difference Dg/g =(1.2 +-1.7)x10^{-7}. We also perform a differential free fall
measurement of atoms in two different hyperfine states, and obtained a result
of Dg/g =(0.4 +-1.2)x10^{-7}.Comment: 4 Pages, 4 figures, accepted for Physical Review Letter
Protein-lipid interactions: correlation of a predictive algorithm for lipid-binding sites with three-dimensional structural data
BACKGROUND: Over the past decade our laboratory has focused on understanding how soluble cytoskeleton-associated proteins interact with membranes and other lipid aggregates. Many protein domains mediating specific cell membrane interactions appear by fluorescence microscopy and other precision techniques to be partially inserted into the lipid bilayer. It is unclear whether these protein-lipid-interactions are dependent on shared protein motifs or unique regional physiochemistry, or are due to more global characteristics of the protein. RESULTS: We have developed a novel computational program that predicts a protein's lipid-binding site(s) from primary sequence data. Hydrophobic labeling, Fourier transform infrared spectroscopy (FTIR), film balance, T-jump, CD spectroscopy and calorimetry experiments confirm that the interfaces predicted for several key cytoskeletal proteins (alpha-actinin, Arp2, CapZ, talin and vinculin) partially insert into lipid aggregates. The validity of these predictions is supported by an analysis of the available three-dimensional structural data. The lipid interfaces predicted by our algorithm generally contain energetically favorable secondary structures (e.g., an amphipathic alpha-helix flanked by a flexible hinge or loop region), are solvent-exposed in the intact protein, and possess favorable local or global electrostatic properties. CONCLUSION: At present, there are few reliable methods to determine the region of a protein that mediates biologically important interactions with lipids or lipid aggregates. Our matrix-based algorithm predicts lipid interaction sites that are consistent with the available biochemical and structural data. To determine whether these sites are indeed correctly identified, and whether use of the algorithm can be safely extended to other classes of proteins, will require further mapping of these sites, including genetic manipulation and/or targeted crystallography
On the uniqueness of -gonal automorphisms of Riemann surfaces
Let be a compact Riemann surface of genus . A cyclic subgroup of
prime order of is called properly -gonal if it has a fixed
point and the quotient surface has genus . We show that if , then a
properly -gonal subgroup of is unique. We also discuss some
related results.Comment: final version, 9 pages, minor improvements, added 2 reference
Two-Dimensional Electron Gas in InGaAs/InAlAs Quantum Wells
We designed and performed low temperature DC transport characterization
studies on two-dimensional electron gases confined in lattice-matched
InGaAs/InAlAs quantum wells grown by
molecular beam epitaxy on InP substrates. The nearly constant mobility for
samples with the setback distance larger than 50nm and the similarity between
the quantum and transport life-time suggest that the main scattering mechanism
is due to short range scattering, such as alloy scattering, with a scattering
rate of 2.2 ps. We also obtain the Fermi level at the
InGaAs/InAlAs surface to be 0.36eV above
the conduction band, when fitting our experimental densities with a
Poisson-Schr\"odinger model.Comment: Accepted in Applied Physics Letter
Bloch oscillations in an aperiodic one-dimensional potential
We study the dynamics of an electron subjected to a static uniform electric
field within a one-dimensional tight-binding model with a slowly varying
aperiodic potential. The unbiased model is known to support phases of localized
and extended one-electron states separated by two mobility edges. We show that
the electric field promotes sustained Bloch oscillations of an initial Gaussian
wave packet whose amplitude reflects the band width of extended states. The
frequency of these oscillations exhibit unique features, such as a sensitivity
to the initial wave packet position and a multimode structure for weak fields,
originating from the characteristics of the underlying aperiodic potential.Comment: 6 pages, 7 figure
Diffusion in disordered systems under iterative measurement
We consider a sequence of idealized measurements of time-separation onto a discrete one-dimensional disordered system. A connection with Markov
chains is found. For a rapid sequence of measurements, a diffusive regime
occurs and the diffusion coefficient is analytically calculated. In a
general point of view, this result suggests the possibility to break the
Anderson localization due to decoherence effects. Quantum Zeno effect emerges
because the diffusion coefficient vanishes at the limit .Comment: 8 pages, 0 figures, LATEX. accepted in Phys.Rev.
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