274 research outputs found
Airloads research study. Volume 2: Airload coefficients derived from wind tunnel data
The development of B-1 aircraft rigid wind tunnel data for use in subsequent tasks of the Airloads Research Study is described. Data from the Rockwell International external structural loads data bank were used to generate coefficients of rigid airload shear, bending moment, and torsion at specific component reference stations or both symmetric and asymmetric loadings. Component stations include the movable wing, horizontal and vertical stabilizers, and forward and aft fuselages. The coefficient data cover a Mach number range from 0.7 to 2.2 for a wing sweep position of 67.5 degree
Airloads research study. Volume 1: Flight test loads acquisition
The acquisition of B-1 aircraft flight loads data for use in subsequent tasks of the Airloads Research Study is described. The basic intent is to utilize data acquired during B-1 aircraft tests, analyze these data beyond the scope of Air Force requirements, and prepare research reports that will add to the technology base for future large flexible aircraft. Flight test data obtained during the airloads survey program included condition-describing parameters, surface pressures, strain gage outputs, and loads derived from pressure and strain gauges. Descriptions of the instrumentation, data processing, and flight load survey program are included. Data from windup-turn and steady yaw maneuvers cover a Mach number range from 0.7 to 2.0 for a wing sweep position of 67.5 deg
The variation of fundamental constants and the role of A=5 and A=8 nuclei on primordial nucleosynthesis
We investigate the effect of a variation of fundamental constants on
primordial element production in big bang nucleosynthesis (BBN). We focus on
the effect of a possible change in the nucleon-nucleon interaction on nuclear
reaction rates involving the A=5 (Li-5 and He-5) and A=8 (Be-8) unstable nuclei
and complement earlier work on its effect on the binding energy of deuterium.
The reaction rates for He3(d,p)He4 and H3(d,n)He4 are dominated by the
properties of broad analog resonances in He-5 and Li-5 compound nuclei
respectively. While the triple alpha process is normally not effective in BBN,
its rate is very sensitive to the position of the "Hoyle state" and could in
principle be drastically affected if Be-8 were stable during BBN. The nuclear
properties (resonance energies in He-5 and Li-5 nuclei, and the binding
energies of Be-8 and D) are all computed in a consistent way using a
microscopic cluster model. The n(p,gamma)d, He3(d,p)He4 and H3(d,n)He4 and
triple-alpha reaction rates are subsequently calculated as a function of the
nucleon-nucleon interaction that can be related to the fundamental constants.
We found that the effect of the variation of constants on the He3(d,p)He4 and
H3(d,n)He4 and triple-alpha reaction rates is not sufficient to induce a
significant effect on BBN, even if Be-8 was stable. In particular, no
significant production of carbon by the triple alpha reaction is found when
compared to standard BBN. We also update our previous analysis on the effect of
a variation of constants on the n(p,gamma)d reaction rate.Comment: 14 pages, 12 figure
Relation between the phenomenological interactions of the algebraic cluster model and the effective two--nucleon forces
We determine the phenomenological cluster--cluster interactions of the
algebraic model corresponding to the most often used effective two--nucleon
forces for the O + system.Comment: Latex with Revtex, 1 figure available on reques
Properties of Be and C deduced from the folding--potential model
The -- differential cross sections are analyzed in the
optical model using a double--folded potential. With the knowledge of this
potential bound and resonance--state properties of --cluster states in
Be and C as well as astrophysical S--factors of
He(,)Be and Be(,)C are
calculated. --widths and B(E2)--values are deduced.Comment: 2 pages LaTeX, 2 figures can be obtained from the author
Alpha-particle condensation in 16O via a full four-body OCM calculation
In order to explore the 4 \alpha-particle condensate state in 16O, we solve a
full four-body equation of motion based on the 4 \alpha OCM (Orthogonality
Condition Model) in a large 4 \alpha model space spanned by Gaussian basis
functions. A full spectrum up to the 0_6^+ state is reproduced consistently
with the lowest six 0^+ states of the experimental spectrum. The 0^+_6 state is
obtained at about 2 MeV above the 4 \alpha breakup threshold and has a dilute
density structure, with a radius of about 5 fm. The state has an appreciably
large \alpha condensate fraction of 61 %, and a large component of
\alpha+12C(0_2^+) configuration, both features being reliable evidence for this
state to be of 4 \alpha condensate nature.Comment: 4 pages, 3 figures and 1 tabl
Alpha cluster condensation in 12C and 16O
A new -cluster wave function is proposed which is of the
-particle condensate type. Applications to C and O show
that states of low density close to the 3 resp. 4 -particle threshold
in both nuclei are possibly of this kind. It is conjectured that all
self-conjugate 4 nuclei may show similar features.Comment: 4 pages, 2 tables, 2 figure
Phenomenological and microscopic cluster models II. Phase transitions
Based on the results of a previous paper (Paper I), by performing the
geometrical mapping via coherent states, phase transitions are investigated and
compared within two algebraic cluster models. The difference between the
Semimicroscopic Algebraic Cluster Model (SACM) and the Phenomenological
Algebraic Cluster Model (PACM) is that the former strictly observes the Pauli
exclusion principle between the nucleons of the individual clusters, while the
latter ignores it. From the technical point of view the SACM is more involved
mathematically, while the formalism of the PACM is closer to that of other
algebraic models with different physical content. First- and second-order phase
transitions are identified in both models, while in the SACM a critical line
also appears. Analytical results are complemented with numerical studies on
{\alpha}-cluster states of the neon-20 and magnesium-24 nuclei.Comment: 11 pages, 13 figures, part two of a two part wor
Phenomenological and microscopic cluster models I. The geometric mapping
The geometrical mapping of algebraic nuclear cluster models is investigated
within the coherent state formalism. Two models are considered: the
Semimicroscopic Algebraic Cluster Model (SACM) and the Phenomenological
Algebraic Cluster Model (PACM), which is a special limit of the SACM. The SACM
strictly observes the Pauli exclusion principle while the PACM does not. The
discussion of the SACM is adapted to the coherent state formalism by
introducing the new SO(3) dynamical symmetry limit and third-order interaction
terms in the Hamiltonian. The potential energy surface is constructed in both
models and it is found that the effects of the Pauli principle can be simulated
by higher-order interaction terms in the PACM. The present study is also meant
to serve as a starting point for investigating phase transitions in the two
algebraic cluster models.Comment: 13 pages, 0 figures, part one of a two part wor
Possible Dibaryons with Strangeness s=-5
In the framework of , the binding energy of the six quark system with
strangeness s=-5 is systematically investigated under the SU(3) chiral
constituent quark model. The single channel calculation with
spins S=0 and 3 and the coupled and channel
calculation with spins S=1 and 2 are considered, respectively. The results show
following observations: In the spin=0 case, is a bound dibaryon
with the binding energy being . In the S=1 case,
is also a bound dibaryon. Its binding energy is ranged from to . In the S=2 and S=3 cases, no evidence of bound dibaryons
are found. The phase shifts and scattering lengths in the S=0 and S=1 cases are
also given.Comment: 10 pages, late
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