23,502 research outputs found
Is There a Significant Difference Between the Results of the Coulomb Dissociation of 8B and the Direct Capture 7Be(p,g)8B Reaction?
Recent claims of the Seattle group of evidence of "slope difference between
CD [Coulomb Dissociation] and direct [capture] results" are based on wrong and
selective data. When the RIKEN2 data are included correctly, and previously
published Direct Capture (DC) data are also included, we observe only a 1.9
sigma difference in the extracted so called "scale independent slope (b)",
considerably smaller than claimed by the Seattle group. The very
parameterization used by the Seattle group to extract the so called b-slope
parameter has no physical foundation. Considering the physical slope (S' =
dS/dE), we observe a 1.0 sigma agreement between slopes (S') measured in CD and
DC, refuting the need for new theoretical investigation. The claim that S17(0)
values extracted from CD data are approximately 10% lower than DC results, is
based on misunderstanding of the CD method. Considering all of the published CD
S17(0) results, with adding back an unconfirmed E2 correction of the MSU data,
yields very consistent S17(0) results that agree with recent DC measurements of
the Seattle and Weizmann groups. The recent correction of the b-slope parameter
(0.25 1/MeV) suggested by Esbensen, Bertsch and Snover was applied to the wrong
b-slope parameter calculated by the Seattle group. When considering the correct
slope of the RIKEN2 data, this correction in fact leads to a very small b-slope
parameter (0.14 1/MeV), less than half the central value observed for DC data,
refuting the need to correct the RIKEN2 data. In particular it confirms that
the E2 contribution in the RIKEN2 data is negligible. The dispersion of
measured S17(0) is mostly due to disagreement among individual DC experiments
and not due to either experimental or theoretical aspects of CD.Comment: Reference 12 amended with an important communication from Dr. Bertsc
Marking parts to aid robot vision
The premarking of parts for subsequent identification by a robot vision system appears to be beneficial as an aid in the automation of certain tasks such as construction in space. A simple, color coded marking system is presented which allows a computer vision system to locate an object, calculate its orientation, and determine its identity. Such a system has the potential to operate accurately, and because the computer shape analysis problem has been simplified, it has the ability to operate in real time
An analytical investigation of a simplified thrust-vector orientation technique for establishing lunar orbits
Simplified thrust vector orientation technique for establishing lunar orbit
Decision-making and problem-solving methods in automation technology
The state of the art in the automation of decision making and problem solving is reviewed. The information upon which the report is based was derived from literature searches, visits to university and government laboratories performing basic research in the area, and a 1980 Langley Research Center sponsored conferences on the subject. It is the contention of the authors that the technology in this area is being generated by research primarily in the three disciplines of Artificial Intelligence, Control Theory, and Operations Research. Under the assumption that the state of the art in decision making and problem solving is reflected in the problems being solved, specific problems and methods of their solution are often discussed to elucidate particular aspects of the subject. Synopses of the following major topic areas comprise most of the report: (1) detection and recognition; (2) planning; and scheduling; (3) learning; (4) theorem proving; (5) distributed systems; (6) knowledge bases; (7) search; (8) heuristics; and (9) evolutionary programming
Role of geometrical symmetry in thermally activated processes in clusters of interacting dipolar moments
Thermally activated magnetization decay is studied in ensembles of clusters
of interacting dipolar moments by applying the master-equation formalism, as a
model of thermal relaxation in systems of interacting single-domain
ferromagnetic particles. Solving the associated master-equation reveals a
breakdown of the energy barrier picture depending on the geometrical symmetry
of structures. Deviations are most pronounced for reduced symmetry and result
in a strong interaction dependence of relaxation rates on the memory of system
initialization. A simple two-state system description of an ensemble of
clusters is developed which accounts for the observed anomalies. These results
follow from a semi-analytical treatment, and are fully supported by kinetic
Monte-Carlo simulations.Comment: 9 pages, 6 figure
A study of the applicability of nucleation theory to quasi-thermodynamic transitions of second and higher Ehrenfest-order
The applicability of classical nucleation theory to second (and higher) order thermodynamic transitions in the Ehrenfest sense has been investigated and expressions have been derived upon which the qualitative and quantitative success of the basic approach must ultimately depend. The expressions describe the effect of temperature undercooling, hydrostatic pressure, and tensile stress upon the critical parameters, the critical nucleus size, and critical free energy barrier, for nucleation in a thermodynamic transition of any general order. These expressions are then specialized for the case of first and second order transitions. The expressions for the case of undercooling are then used in conjunction with literature data to estimate values for the critical quantities in a system undergoing a pseudo-second order transition (the glass transition in polystyrene). Methods of estimating the interfacial energy gamma in systems undergoing a first and second order transition are also discussed
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