14,120 research outputs found
Liner environment effects study
The Liner Environment Effects Study Program is aimed at establishing a broad heat transfer data base under controlled experimental conditions by quantifying the effects of the combustion system conditions on the combustor liner thermal loading and on the flame radiation characteristics. Five liner concepts spanning the spectrum of liner design technology from the very simple to the most advanced concepts are investigated. These concepts comprise an uncooled liner, a conventional film cooled liner, an impingement/film cooled liner, a laser drilled liner approaching the concept of a porous wall, and a siliconized silicon carbide ceramic liner. Effect of fuel type is covered by using fuels containing 11.8, 12.8, and 14% hydrogen. Tests at 100, 200, and 300 psia provide a basis for evaluating the effect of pressure on the heat transfer. The effects of the atomization quality and spray characteristics are examined by varying the fuel spray Sauter mean diameter and the spray angle. Additional varied parameters include reference velocity, a wide range of equivalence ratio, cooling flow rate, coolant temperature and the velocity of the coolant stream on the backside of the liner
Environmental Effects on Face Recognition in Smartphones
Face recognition is convenient for user authentication on smartphones as it offers several advantages suitable for mobile environments. There is no need to remember a numeric code or password or carry tokens. Face verification allows the unlocking of the smartphone, pay bills or check emails through looking at the smartphone. However, devices mobility also introduces a lot of factors that may influence the biometric performance mainly regarding interaction and environment. Scenarios can vary significantly as there is no control of the surroundings. Noise can be caused by other people appearing on the background, by different illumination conditions, by different users’ poses and through many other reasons. User-interaction with biometric systems is fundamental: bad experiences may derive to unwillingness to use the technology. But how does the environment influence the quality of facial images? And does it influence the user experience with face recognition? In order to answer these questions, our research investigates the user-biometric system interaction from a non-traditional point of view: we recreate reallife scenarios to test which factors influence the image quality in face recognition and, quantifiably, to what extent. Results indicate the variability in face recognition performance when varying environmental conditions using smartphones
Derived environment effects: A representational approach
Derived environment effects involve either overapplication or underapplication of phonological rules in phonological or morphological environments. This paper focuses on underapplication effects in both phonological and morphological environments, which are treated as resulting from representational differences between derived and non-derived environments at the appropriate level. The Government and Dependency Phonology notions of head and dependent are utilised to this end. Thus, phonologically derived environment effects result from melodic structure that differentiates branching from immediate dominance relations between elements, allowing phonological processes to target a segment of one melodic configuration to the exclusion of another. Morphologically derived environment effects, on the other hand, involve representational differences at the constituent structure level, corresponding to the fact that morphological effects are a result of junctural or morpheme-integrity effects. In the latter case, head-dependent relations are defined as holding over domains, thereby differentiating affixal from non-affixal material, while in the former junctural effects the representational difference is defined at the CV tier, with phonological processes being sensitive to the presence of empty V and C positions. © 2008 Elsevier B.V. All rights reserved
New chemical evolution analytical solutions including environment effects
In the last years, more and more interest has been devoted to analytical
solutions, including inflow and outflow, to study the metallicity enrichment in
galaxies. In this framework, we assume a star formation rate which follows a
linear Schmidt law, and we present new analytical solutions for the evolution
of the metallicity (Z) in galaxies. In particular, we take into account
environmental effects including primordial and enriched gas infall, outflow,
different star formation efficiencies, and galactic fountains. The enriched
infall is included to take into account galaxy-galaxy interactions. Our main
results can be summarized as: i) when a linear Schmidt law of star formation is
assumed, the resulting time evolution of the metallicity Z is the same either
for a closed-box model or for an outflow model. ii) The mass-metallicity
relation for galaxies which suffer a chemically enriched infall, originating
from another evolved galaxy with no pre-enriched gas, is shifted down in
parallel at lower Z values, if compared the closed box model. iii) When a
galaxy suffers at the same time a primordial infall and a chemically enriched
one, the primordial infall always dominates the chemical evolution. iv) We
present new solutions for the metallicity evolution in a galaxy which suffers
galactic fountains and an enriched infall from another galaxy at the same time.
The analytical solutions presented here can be very important to study the
metallicity (oxygen), which is measured in high-redshift objects. These
solutions can be very useful: a) in the context of cosmological semi-analytical
models for galaxy formation and evolution, and b) for the study of compact
groups of galaxies.Comment: Accepted for publication in MNRA
Environment effects on the electric conductivity of the DNA
We present a theoretical analysis of the environment effects on charge
transport in double-stranded synthetic poly(G)-poly(C) DNA molecules attached
to two ideal leads. Coupling of the DNA to the environment results in two
effects: (i) localization of carrier functions due to the static disorder and
(ii) phonon-induced scattering of the carrier between these localized states,
resulting in hopping conductivity. A nonlinear Pauli master equation for
populations of localized states is used to describe the hopping transport and
calculate the electric current as a function of the applied bias. We
demonstrate that, although the electronic gap in the density of states shrinks
as the disorder increases, the voltage gap in the characteristics becomes
wider. Simple physical explanation of this effect is provided.Comment: 8 pages, 2 figures, to appear in J. Phys.: Condens. Matte
Microscopic Approach to Analyze Solar-Sail Space-Environment Effects
Near-sun space-environment effects on metallic thin films solar sails as well
as hollow-body sails with inflation fill gas are considered. Analysis of
interaction of the solar radiation with the solar sail materials is presented.
This analysis evaluates worst-case solar radiation effects during
solar-radiation-pressure acceleration. The dependence of the thickness of solar
sail on temperature and on wavelength of the electromagnetic spectrum of solar
radiation is investigated. Physical processes of the interaction of photons,
electrons, protons and helium nuclei with sail material atoms and nuclei, and
inflation fill gas molecules are analyzed. Calculations utilized conservative
assumptions with the highest values for the available cross sections for
interactions of solar photons, electrons and protons with atoms, nuclei and
hydrogen molecules. It is shown that for high-energy photons, electrons and
protons the beryllium sail is mostly transparent. Sail material will be
partially ionized by solar UV and low-energy solar electrons. For a hollow-body
photon sail effects including hydrogen diffusion through the solar sail walls,
and electrostatic pressure is considered. Electrostatic pressure caused by the
electrically charged sail's electric field may require mitigation since sail
material tensile strength decreases with elevated temperature.Comment: 10 pages, 6 figures. Talk given on the 59 International Astronautical
Congress, Glasgow, Scotland, 29 September - 2 October, 200
Symmetry and environment effects on rectification mechanisms in quantum pumps
We consider a paradigmatic model of quantum pumps and discuss its
rectification properties in the framework of a symmetry analysis proposed for
ratchet systems. We discuss the role of the environment in breaking
time-reversal symmetry and the possibility of a finite directed current in the
Hamiltonian limit of annular systems.Comment: To appear as Rapid Communication in PR
Sequence composition and environment effects on residue fluctuations in protein structures
The spectrum and scale of fluctuations in protein structures affect the range
of cell phenomena, including stability of protein structures or their
fragments, allosteric transitions and energy transfer. The study presents a
statistical-thermodynamic analysis of relationship between the sequence
composition and the distribution of residue fluctuations in protein-protein
complexes. A one-node-per residue elastic network model accounting for the
nonhomogeneous protein mass distribution and the inter-atomic interactions
through the renormalized inter-residue potential is developed. Two factors, a
protein mass distribution and a residue environment, were found to determine
the scale of residue fluctuations. Surface residues undergo larger fluctuations
than core residues, showing agreement with experimental observations. Ranking
residues over the normalized scale of fluctuations yields a distinct
classification of amino acids into three groups. The structural instability in
proteins possibly relates to the high content of the highly fluctuating
residues and a deficiency of the weakly fluctuating residues in irregular
secondary structure elements (loops), chameleon sequences and disordered
proteins. Strong correlation between residue fluctuations and the sequence
composition of protein loops supports this hypothesis. Comparing fluctuations
of binding site residues (interface residues) with other surface residues shows
that, on average, the interface is more rigid than the rest of the protein
surface and Gly, Ala, Ser, Cys, Leu and Trp have a propensity to form more
stable docking patches on the interface. The findings have broad implications
for understanding mechanisms of protein association and stability of protein
structures.Comment: 8 pages, 4 figure
Nonlinear model predictive control applied to multivariable thermal and chemical control of selective catalytic reduction aftertreatment
Manufacturers of diesel engines are under increasing pressure to meet progressively stricter NOx emissions limits. A key NOx abatement technology is selective catalytic reduction (SCR) in which ammonia, aided by a catalyst, reacts with NOx in the exhaust stream to produce nitrogen and water. The conversion efficiency is temperature dependent: at low temperature, reaction rates are temperature limited, resulting in suboptimal NOx removal, whereas at high temperatures, they are mass transfer limited. Maintaining sufficiently high temperature to allow maximal conversion is a challenge, particularly after cold start, as well as during conditions in which exhaust heat is insufficient, such as periods of low load or idling. In this work, a nonlinear model predictive controller simultaneously manages urea injection and power to an electric catalyst heater, in the presence of constraints.<br/
Combined space environment effects on typical spacecraft window materials final report, jun. 1964 - jun. 1965
Simulated space radiation environment effects on Apollo spacecraft window material
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