10,991 research outputs found
The energy efficient engine project
The Energy Efficient Engine Project is directed at providing, by 1984, the advanced technologies which could be used for a generation of fuel conservative turbofan engines. The project is conducted through contracts with the General Electric Company and Pratt and Whitney Aircraft. The scope of the entire project and the current status of these efforts are summarized. A description of the preliminary designs of the fully developed engines is included and the potential benefits of these advanced engines, as well as highlights of some of the component technology efforts conducted to date, are discussed
Design approaches to more energy efficient engines
The status of NASA's Energy Efficient Engine Project, a comparative government-industry effort aimed at advancing the technology base for the next generation of large turbofan engines for civil aircraft transports is summarized. Results of recently completed studies are reviewed. These studies involved selection of engine cycles and configurations that offer potential for at least 12% lower fuel consumption than current engines and also are economically attractive and environmentally acceptable. Emphasis is on the advancements required in component technologies and systems design concepts to permit future development of these more energy efficient engines
Southern Sky Redshift Survey: Clustering of Local Galaxies
We use the two-point correlation function to calculate the clustering
properties of the recently completed SSRS2 survey. The redshift space
correlation function for the magnitude-limited SSRS2 is given by xi(s)=(s/5.85
h-1 Mpc)^{-1.60} for separations between 2 < s < 11 h-1 Mpc, while our best
estimate for the real space correlation function is xi(r) = (r/5.36 h-1
Mpc)^{-1.86}. Both are comparable to previous measurements using surveys of
optical galaxies over much larger and independent volumes. By comparing the
correlation function calculated in redshift and real space we find that the
redshift distortion on intermediate scales is small. This result implies that
the observed redshift-space distribution of galaxies is close to that in real
space, and that beta = Omega^{0.6}/b < 1, where Omega is the cosmological
density parameter and b is the linear biasing factor for optical galaxies. We
also use the SSRS2 to study the dependence of xi on the internal properties of
galaxies. We confirm earlier results that luminous galaxies (L>L*) are more
clustered than sub-L* galaxies and that the luminosity segregation is
scale-independent. We find that early types are more clustered than late types,
but that in the absence of rich clusters, the relative bias between early and
late types in real space, is not as strong as previously estimated.
Furthermore, both morphologies present a luminosity-dependent bias, with the
early types showing a slightly stronger dependence on luminosity. We also find
that red galaxies are significantly more clustered than blue ones, with a mean
relative bias stronger than that seen for morphology. Finally, we find that the
relative bias between optical and iras galaxies in real space is b_o/b_I
1.4.Comment: 43 pages, uses AASTeX 4.0 macros. Includes 8 tables and 16 Postscript
figures, updated reference
Complementarity and Scientific Rationality
Bohr's interpretation of quantum mechanics has been criticized as incoherent
and opportunistic, and based on doubtful philosophical premises. If so Bohr's
influence, in the pre-war period of 1927-1939, is the harder to explain, and
the acceptance of his approach to quantum mechanics over de Broglie's had no
reasonable foundation. But Bohr's interpretation changed little from the time
of its first appearance, and stood independent of any philosophical
presuppositions. The principle of complementarity is itself best read as a
conjecture of unusually wide scope, on the nature and future course of
explanations in the sciences (and not only the physical sciences). If it must
be judged a failure today, it is not because of any internal inconsistency.Comment: 29 page
A physics-based life prediction methodology for thermal barrier coating systems
A novel mechanistic approach is proposed for the prediction of the life of
thermal barrier coating (TBC) systems. The life prediction methodology is based
on a criterion linked directly to the dominant failure mechanism. It relies on
a statistical treatment of the TBC's morphological characteristics,
non-destructive stress measurements and on a continuum mechanics framework to
quantify the stresses that promote the nucleation and growth of microcracks
within the TBC. The last of these accounts for the effects of TBC constituents'
elasto-visco-plastic properties, the stiffening of the ceramic due to sintering
and the oxidation at the interface between the thermally insulating yttria
stabilized zirconia (YSZ) layer and the metallic bond coat. The mechanistic
approach is used to investigate the effects on TBC life of the properties and
morphology of the top YSZ coating, metallic low-pressure plasma sprayed bond
coat and the thermally grown oxide. Its calibration is based on TBC damage
inferred from non-destructive fluorescence measurements using
piezo-spectroscopy and on the numerically predicted local TBC stresses
responsible for the initiation of such damage. The potential applicability of
the methodology to other types of TBC coatings and thermal loading conditions
is also discussed
SME innovation and learning: the role of networks and crisis events
Purpose:
To contribute to the literature on innovation and entrepreneurial learning by exploring how SMEs learn and innovate, how they use of both formal and informal learning and in particular the role of networks and crisis events within their learning experience.
Design/methodology/approach:
Mixed method study, comprising 13 focus groups, over 1000 questionnaire responses from SME mangers, 13 focus groups and 20 case studies derived from semi-structured interviews.
Findings:
SMEs have a strong commitment to learning, and a shared vision. Much of this learning is informal through network events, mentoring or coaching. SMEs that are innovative are significantly more committed to learning than those which are less innovative, seeing employee learning as an investment. Innovative SMEs are more likely to have a shared vision, be open-minded and to learn from crises, being able to reflect on their experiences.
Implications for research:
There is a need for further process driven qualitative research to understand the interrelationship between, particularly informal, learning, crisis events and SME innovation.
Implications for practice:
SME owners need opportunities and time for reflection as a means of stimulating personal learning â particularly the opportunity to learn from crisis events. Access to mentors (often outside the business) can be important here, as are informal networks.
Originality/value:
This is one of the first mixed method large scale studies to explore the relationship between SME innovation and learning, highlighting the importance of informal learning to innovation and the need for SME leaders to foster this learning as part of a shared organisational vision
The infrared luminosity function of galaxies at redshifts z=1 and z~2 in the GOODS fields
We present the rest-frame 8 micron luminosity function (LF) at redshifts z=1
and ~2, computed from Spitzer 24 micron-selected galaxies in the GOODS fields
over an area of 291 sq. arcmin. Using classification criteria based on X-ray
data and IRAC colours, we identify the AGN in our sample. The rest-frame 8
micron LF for star-forming galaxies at redshifts z=1 and ~2 have the same shape
as at z~0, but with a strong positive luminosity evolution. The number density
of star-forming galaxies with log_{10}(nu L_nu(8 micron))>11 increases by a
factor >250 from redshift z~0 to 1, and is basically the same at z=1 and ~2.
The resulting rest-frame 8 micron luminosity densities associated with star
formation at z=1 and ~2 are more than four and two times larger than at z~0,
respectively. We also compute the total rest-frame 8 micron LF for star-forming
galaxies and AGN at z~2 and show that AGN dominate its bright end, which is
well-described by a power-law. Using a new calibration based on Spitzer
star-forming galaxies at 0<z<0.6 and validated at higher redshifts through
stacking analysis, we compute the bolometric infrared (IR) LF for star-forming
galaxies at z=1 and ~2. We find that the respective bolometric IR luminosity
densities are (1.2+/-0.2) x 10^9 and (6.6^{+1.2}_{-1.0}) x 10^8 L_sun Mpc^{-3},
in agreement with previous studies within the error bars. At z~2, around 90% of
the IR luminosity density associated with star formation is produced by
luminous and ultraluminous IR galaxies (LIRG and ULIRG), with the two
populations contributing in roughly similar amounts. Finally, we discuss the
consistency of our findings with other existing observational results on galaxy
evolution.Comment: Accepted for publication in the ApJ. 33 pages, 15 figures. Uses
emulateap
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