18,246 research outputs found
ENERGY EFFICIENCY OF DIFFERENT TENNIS RACKET STIFFNESS AND STRING TENSION DUE TO CENTER AND OFF-CENTER IMPACT
The purpose of this study was to investigate the power of vibration responses and moments of different racket flexibilities and string tensions following center and off-center impacts. Three rackets, classed as stiff, medium, and flexible by their manufacturers, were strung at three string tensions and subjected to 15 trials. The rackets were gripped on a KISTLER force plate and impacted at designated areas by a rigid ball. The stiff racket had smaller powers of vibration and twisting moment for each string tension in offcenter impact. The largest power of vibration and twisting moment occurred respectively in the flexible racket strung with 50pound and medium racket strung with 70 pound in offcenter impact
Low Momentum Nucleon-Nucleon Interactions and Shell-Model Calculations
In the last few years, the low-momentum nucleon-nucleon (NN) interaction
V-low-k derived from free-space NN potentials has been successfully used in
shell-model calculations. V-low-k is a smooth potential which preserves the
deuteron binding energy as well as the half-on-shell T-matrix of the original
NN potential up to a momentum cutoff Lambda. In this paper we put to the test a
new low-momentum NN potential derived from chiral perturbation theory at
next-to-next-to-next-to-leading order with a sharp low-momentum cutoff at 2.1
fm-1. Shell-model calculations for the oxygen isotopes using effective
hamiltonians derived from both types of low-momentum potential are performed.
We find that the two potentials show the same perturbative behavior and yield
very similar results.Comment: 8 pages, 8 figures, to be published in Physical Review
Measurement of opaque film thickness
The theoretical and experimental framework for thickness measurements of thin metal films by low frequency thermal waves is described. Although it is assumed that the films are opaque and the substrates are comparatively poor thermal conductors, the theory is easily extended to other cases of technological interest. A brief description is given of the thermal waves and the experimental arrangement and parameters. The usefulness of the technique is illustrated for making absolute measurements of the thermal diffusivities of isotropic substrate materials. This measurement on pure elemental solids provides a check on the three dimensional theory in the limiting case of zero film thickness. The theoretical framework is then presented, along with numerical calculations and corresponding experimental results for the case of copper films on a glass substrate
Determining the sign of at long baseline neutrino experiments
Recently it is advocated that high intensity and low energy neutrino beams should be built to probe the mixing angle to
a level of a few parts in . Experiments using such beams will have better
signal to background ratio in searches for oscillations. We
propose that such experiments can also determine the sign of even
if the beam consists of {\it neutrinos} only. By measuring the transitions in two different energy ranges, the effects due to
propagation of neutrinos through earth's crust can be isolated and the sign of
can be determined. If the sensitivity of an experiment to
is , then the same experiment is automatically sensitive to matter
effects and the sign of for values of .Comment: Title changed and paper rewritten. 4 pages, 1 figure, revte
Hermitian quark mass matrices with four texture zeros
We provide a complete and systematic analysis of hermitian, hierarchical
quark mass matrices with four texture zeros. Using triangular mass matrices,
each pattern of texture zeros is readily shown to lead to a definite relation
between the CKM parameters and the quark masses. Nineteen pairs are found to be
consistent with present data, and one other is marginally acceptable. In
particular, no parallel structure between the up and down mass matrices is
found to be favorable with data.Comment: 18 pages, no figure, references [8] and [10] adde
Probing neutrino mass hierarchies and with supernova neutrinos
We investigate the feasibility of probing the neutrino mass hierarchy and the
mixing angle with the neutrino burst from a future supernova. An
inverse power-law density with varying is adopted in the
analysis as the density profile of a typical core-collapse supernova. The
survival probabilities of and are shown to reduce to
two-dimensional functions of and . It is found that in the
parameter space, the 3D plots of the probability
functions exhibit highly non-trivial structures that are sensitive to the mass
hierarchy, the mixing angle , and the value of . The conditions
that lead to observable differences in the 3D plots are established. With the
uncertainty of considered, a qualitative analysis of the Earth matter
effect is also included.Comment: 16 pages, 3 figures. Ref [11] added, and some typos correcte
Solar Neutrinos with Three Flavor Mixings
The recent 71Ga solar neutrino observation is combined with the 37Cl and
Kamiokande-II observations in an analysis for neutrino masses and mixings. The
allowed parameter region is found for matter enhanced mixings among all three
neutrino flavors. Distortions of the solar neutrino spectrum unique to three
flavors are possible and may be observed in continuing and next generation
experiments.Comment: August 1992 (Revised) PURD-TH-92-
Gravitons and Lightcone Fluctuations II: Correlation Functions
A model of a fluctuating lightcone due to a bath of gravitons is further
investigated. The flight times of photons between a source and a detector may
be either longer or shorter than the light propagation time in the background
classical spacetime, and will form a Gaussian distribution centered around the
classical flight time. However, a pair of photons emitted in rapid succession
will tend to have correlated flight times. We derive and discuss a correlation
function which describes this effect. This enables us to understand more fully
the operational significance of a fluctuating lightcone. Our results may be
combined with observational data on pulsar timing to place some constraints on
the quantum state of cosmological gravitons.Comment: 16 pages and two figures, uses eps
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