14,031 research outputs found
A concept for universal pliers
By modification in existing design, pliers can be made to have one pair of handles that will accept number of different jaws. Concept is useful for light to medium duty service. Complete set of jaws may be made to suit specific hobbies or applications
A Supersymmetric Twin Higgs
We present a supersymmetric realization of the twin Higgs mechanism, which
cancels off all contributions to the Higgs mass generated above a scale f.
Radiative corrections induced by the top quark sector lead to a breaking of the
twin sector electroweak symmetry at a scale f ~ TeV. In our sector, below the
scale f, these radiative corrections from the top quark are present but greatly
weakened, naturally allowing a Z boson mass an order of magnitude below f, even
with a top squark mass of order 1 TeV and a messenger scale near the Planck
mass. A sufficient quartic interaction for our Higgs boson arises from the
usual gauge contribution together with a radiative contribution from a heavy
top squark. The mechanism requires the presence of an SU(2)-adjoint superfield,
and can be simply unified. Naturalness in these theories is usually associated
with light winos and sleptons, and is largely independent of the scale of the
colored particles. The assumption of unification naturally predicts the
existence of many exotic fields. The theory often has particles which may be
stable on collider timescales, including an additional color octet superfield.
In the limit that m_SUSY >> f, the mechanism yields a UV completion of the
non-supersymmetric twin Higgs, but with the notable improvement of a tree-level
quartic for the standard model Higgs. In this framework, a successful UV
completion requires the existence of new charged fields well below the scale f.Comment: 20 page
Turbomachinery technology for high-speed civil flight
NASA Lewis' research and technology efforts applicable to turbomachinery for high-speed flight are discussed. The potential benefits and cycle requirements for advanced variable cycle engines and the supersonic throughflow fan engine for a high-speed civil transport application are presented. The supersonic throughflow fan technology program is discussed. Technology efforts in the basic discipline areas addressing the severe operating conditions associated with high-speed flight turbomachinery are reviewed. Included are examples of work in internal fluid mechanics, high-temperature materials, structural analysis, instrumentation and controls
Impact and promise of NASA aeropropulsion technology
The aeropropulsion industry in the U.S. has established an enviable record of leading the world in aeropropulsion for commercial and military aircraft. NASA's aeropropulsion program (primarily conducted through the Lewis Research Center) has significantly contributed to that success through research and technology advances and technology demonstration. Some past NASA contributions to engines in current aircraft are reviewed, and technologies emerging from current research programs for the aircraft of the 1990's are described. Finally, current program thrusts toward improving propulsion systems in the 2000's for subsonic commercial aircraft and higher speed aircraft such as the High-Speed Civil Transport and the National Aerospace Plane are discussed
Mission F, LM descent/phasing summary document
Lunar module descent/phasing summary for mission
Probing Satellite Quenching With Galaxy Clustering
Satellites within simulated massive clusters are significantly spatially
correlated with each other, even when those satellites are not gravitationally
bound to each other. This correlation is produced by satellites that entered
their hosts relatively recently, and is undetectable for satellites that have
resided in their hosts for multiple dynamical timescales. Therefore, a
measurement of clustering statistics of cluster satellites may be used to
determine the typical accretion redshifts of those satellites into their
observed hosts. We argue that such measurements may be used to determine the
fraction of satellite galaxies that were quenched by their current hosts,
thereby discriminating among models for quenching of star formation in
satellite galaxies.Comment: 7 page
Statistical properties of fractures in damaged materials
We introduce a model for the dynamics of mud cracking in the limit of of
extremely thin layers. In this model the growth of fracture proceeds by
selecting the part of the material with the smallest (quenched) breaking
threshold. In addition, weakening affects the area of the sample neighbour to
the crack. Due to the simplicity of the model, it is possible to derive some
analytical results. In particular, we find that the total time to break down
the sample grows with the dimension L of the lattice as L^2 even though the
percolating cluster has a non trivial fractal dimension. Furthermore, we obtain
a formula for the mean weakening with time of the whole sample.Comment: 5 pages, 4 figures, to be published in Europhysics Letter
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