36,141 research outputs found
Spin Structure of the Proton
By assuming that there is no significant intrinsic polarization of the gluon,
we have computed the polarized quark contributions to the proton's spin under
SU(3) flavor symmetry breaking for the polarized sea and have performed a
global leading-order QCD fit to obtain the spin-dependent quark distributions,
which could be used as input for analyzing lepton-hadron and hadron-hadron
collisions.Comment: 13 pages, NCKU-HEP/94-0
Structural Aspects of the Proton in the Chiral Quark Model
We calculate with chiral symmetry the parton contents of the proton based on
a two-component wave function. The calculation results give significant
sea-quark contents and, especially, the intrinsic gluon polarization produced
at a more fundamental level.Comment: 10 pages, LaTe
Perturbation of coupling matrices and its effect on the synchronizability in arrays of coupled chaotic systems
In a recent paper, wavelet analysis was used to perturb the coupling matrix
in an array of identical chaotic systems in order to improve its
synchronization. As the synchronization criterion is determined by the second
smallest eigenvalue of the coupling matrix, the problem is
equivalent to studying how of the coupling matrix changes with
perturbation. In the aforementioned paper, a small percentage of the wavelet
coefficients are modified. However, this result in a perturbed matrix where
every element is modified and nonzero. The purpose of this paper is to present
some results on the change of due to perturbation. In particular,
we show that as the number of systems , perturbations which only
add local coupling will not change . On the other hand, we show that
there exists perturbations which affect an arbitrarily small percentage of
matrix elements, each of which is changed by an arbitrarily small amount and
yet can make arbitrarily large. These results give conditions on
what the perturbation should be in order to improve the synchronizability in an
array of coupled chaotic systems. This analysis allows us to prove and explain
some of the synchronization phenomena observed in a recently studied network
where random coupling are added to a locally connected array. Finally we
classify various classes of coupling matrices such as small world networks and
scale free networks according to their synchronizability in the limit.Comment: 7 pages, 2 figures, 1 tabl
Parametric amplification in single-walled carbon nanotube nanoelectromechanical resonators
The low quality factor (Q) of Single-walled carbon nanotube (SWNT) resonators
has limited their sensitivity in sensing application. To this end, we employ
the technique of parametric amplification by modulating the spring constant of
SWNT resonators at twice the resonant frequency, and achieve 10 times Q
enhancement. The highest Q obtained at room temperature is around ~700, which
is 3-4 times better than previous Q record reported for doubly-clamped SWNT
resonators. Furthermore, efficient parametric amplification is found to only
occur in the catenary vibration regime. Our results open up the possibility to
employ light-weight and high-Q carbon nanotube resonators in single molecule
and atomic mass sensing.Comment: 14 pages, 3 figure
- âŠ