310 research outputs found
Avionics systems integration technology
A very dramatic and continuing explosion in digital electronics technology has been taking place in the last decade. The prudent and timely application of this technology will provide Army aviation the capability to prevail against a numerically superior enemy threat. The Army and NASA have exploited this technology explosion in the development and application of avionics systems integration technology for new and future aviation systems. A few selected Army avionics integration technology base efforts are discussed. Also discussed is the Avionics Integration Research Laboratory (AIRLAB) that NASA has established at Langley for research into the integration and validation of avionics systems, and evaluation of advanced technology in a total systems context
Fermion Masses and Coupling Unification in E6. Life in the Desert
We present an Grand Unified model with a realistic pattern of fermion
masses. All standard model fermions are unified in three fundamental 27-plets
(i.e. supersymmetry is not invoked), which involve in addition right handed
neutrinos and three families of vector like heavy quarks and leptons. The
lightest of those can lie in the low TeV range, being accessible to future
collider experiments. Due to the high symmetry, the masses and mixings of all
fermions are closely related. The new heavy fermions play a crucial role for
the quark and lepton mass matrices and the bilarge neutrino oscillations. In
all channels generation mixing and violation arise from a single
antisymmetric matrix. The breaking proceeds via an intermediate energy
region with SU(3)_L\tm SU(3)_R\tm SU(3)_C gauge symmetry and a discrete
left-right symmetry. This breaking pattern leads in a straightforward way to
the unification of the three gauge coupling constants at high scales, providing
for a long proton lifetime. The model also provides for the unification of the
top, bottom and tau Yukawa couplings and for new interesting relations in
flavor and generation space.Comment: RevTex4, three ps figures, some correction
Compensation for harm caused by nuclear installations: what’s the damage?
This is the author accepted manuscript. The final version is available from Emerald via the DOI in this record.Purpose: This paper aims to explain the changes to the liability regime for nuclear installations before reviewing the traditional heads of damage under the 1965 Act. It argues that while there is some welcome clarification of what amounts to an “occurrence” in the purposes of the 1965 Act, disappointingly, little has been done to clarify how concepts of personal injury and property damage under the Act sit alongside traditional tort notions leaving the law highly dependent on earlier, but not always consistent, case law. The paper then goes on to consider the impact of the new categories of compensation, introduced by the Order, evaluating the extent to which these draw upon EU law structures for environmental impairment liability. Again, it questions whether this approach will achieve sufficient clarity and certainty. Design/methodology/approach: This paper is a desk-based legal research. Findings: This study is a discussion of statutory material and case law. Originality/value: This paper is a first in-depth treatment of changes to liability principles in the Nuclear Installations Act 1965
Experimental cross sections of Ho 165 (α,n) Tm 168 and Er 166 (α,n) Yb 169 for optical potential studies relevant for the astrophysical γ process
Background: Optical potentials are crucial ingredients for the prediction of nuclear reaction rates needed in simulations of the astrophysical γ process. Associated uncertainties are particularly large for reactions involving α particles. This includes (γ,α) reactions which are of special importance in the γ process. Purpose: The measurement of (α,n) reactions allows for an optimization of currently used α-nucleus potentials. The reactions Ho165(α,n) and Er166(α,n) probe the optical model in a mass region where γ process calculations exhibit an underproduction of p nuclei which is not yet understood. Method: To investigate the energy-dependent cross sections of the reactions Ho165(α,n) and Er166(α,n) close to the reaction threshold, self-supporting metallic foils were irradiated with α particles using the FN tandem Van de Graaff accelerator at the University of Notre Dame. The induced activity was determined afterwards by monitoring the specific β-decay channels. Results: Hauser-Feshbach predictions with a widely used global α potential describe the data well at energies where the cross sections are almost exclusively sensitive to the α widths. Increasing discrepancies appear towards the reaction threshold at lower energy. Conclusions: The tested global α potential is suitable at energies above 14 MeV, while a modification seems necessary close to the reaction threshold. Since the γ and neutron widths show non-negligible impact on the predictions, complementary data are required to judge whether or not the discrepancies found can be solely assigned to the α width. © 2014 American Physical Society.Peer reviewedFinal Accepted Versio
Non-local anomaly of the axial-vector current for bound states
We demonstrate that the amplitude does not vanish in the limit of zero quark masses. This
represents a new kind of violation of the classical equation of motion for the
axial current and should be interpreted as the axial anomaly for bound states.
The anomaly emerges in spite of the fact that the one loop integrals are
ultraviolet-finite as guaranteed by the presence of the bound-state wave
function. As a result, the amplitude behaves like in the limit of
a large momentum of the current. This is to be compared with the amplitude
which remains
finite in the limit .
The observed effect leads to the modification of the classical equation of
motion of the axial-vector current in terms of the non-local operator and can
be formulated as a non-local axial anomaly for bound states.Comment: revtex, 4 pages, numerical value for in Eq. (19) is
corrected, Eqs. (22) and (23) are modified. New references added. Results
remain unchange
Remote sensing: Physical principles, sensors and products, and the LANDSAT
Techniques of data acquisition by remote sensing are introduced in this teaching aid. The properties of the elements involved (radiant energy, topograph, atmospheric attenuation, surfaces, and sensors) are covered. Radiometers, photography, scanners, and radar are described as well as their products. Aspects of the LANDSAT system examined include the characteristics of the satellite and its orbit, the multispectral band scanner, and the return beam vidicon. Pixels (picture elements), pattern registration, and the characteristics, reception, and processing of LANDSAT imagery are also considered
Hierarchy plus anarchy in quark masses and mixings
We introduce a new parameterisation of the effect of unknown corrections from
new physics on quark and lepton mass matrices. This parameterisation is used in
order to study how the hierarchies of quark masses and mixing angles are
modified by random perturbations of the Yukawa matrices. We discuss several
examples of flavour relations predicted by different textures, analysing how
these relations are influenced by the random perturbations. We also comment on
the unlikely possibility that unknown corrections contribute significantly to
the hierarchy of masses and mixings.Comment: LaTeX, 18 pages, 16 PS figure
Combining exclusive semi-leptonic and hadronic B decays to measure |V_ub|
The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the
rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little
theoretical uncertainty, provided the hadronic form factor for the B -> pi
transition can be measured from some other B decay. In here, we suggest using
the decay B -> pi J\psi. This is a color suppressed decay, and it cannot be
properly described within the usual factorization approximation; we use instead
a simple and very general phenomenological model for the b d J\psi vertex. In
order to relate the hadronic form factors in the B -> pi J\psi and B -> pi + l
+ antineutrino_l decays, we use form factor relations that hold for
heavy-to-light transitions at large recoil.Comment: Latex, 7 pages, no figure
Form factors of heavy-to-light B decays at large recoil
General relations between the form factors of B decays to light mesons are
derived using the heavy quark and large recoil expansion. On their basis the
complete account of contributions of second order in the ratio of the light
meson mass to the large recoil energy is performed. Both ground and excited
final meson states are considered. It is shown that most of the known form
factor relations remain valid after the inclusion of quadratic mass
corrections. The validity of some of such relations requires additional
equalities for the helicity amplitudes. It is found that all these relations
and equalities are fulfilled in the relativistic quark model based on the
quasipotential approach in quantum field theory. The contribution of 1/m_b
corrections to the branching fraction of the rare radiative B decay is
discussed.Comment: 23 pages, revte
- …