2,924 research outputs found
Study of limit cycles and stability of a space vehicle attitude control system
Limit cycles and stability of three-axis space vehicle attitude control syste
Comprehension and Rate: Oral vs. Silent Reading for Low Achievers
This investigator sought to examine the influence of oral and silent reading behavior on the reading rate and comprehension levels of the learner. Two questions were posed for investigation: 1. Do low achieving fourth graders read significantly more rapidly silently or orally? 2. Do low achieving fourth graders comprehend materials significantly better after having read orally or after having read silently
Counting approximately-shortest paths in directed acyclic graphs
Given a directed acyclic graph with positive edge-weights, two vertices s and
t, and a threshold-weight L, we present a fully-polynomial time
approximation-scheme for the problem of counting the s-t paths of length at
most L. We extend the algorithm for the case of two (or more) instances of the
same problem. That is, given two graphs that have the same vertices and edges
and differ only in edge-weights, and given two threshold-weights L_1 and L_2,
we show how to approximately count the s-t paths that have length at most L_1
in the first graph and length at most L_2 in the second graph. We believe that
our algorithms should find application in counting approximate solutions of
related optimization problems, where finding an (optimum) solution can be
reduced to the computation of a shortest path in a purpose-built auxiliary
graph
Single shot measurement of a silicon single electron transistor
We have fabricated a custom cryogenic Complementary Metal-Oxide-Semiconductor
(CMOS) integrated circuit that has a higher measurement bandwidth compared with
conventional room temperature electronics. This allowed implementing single
shot operations and observe the real-time evolution of the current of a
phosphorous-doped silicon single electron transistor that was irradiated with a
microwave pulse. Relaxation times up to 90 us are observed, suggesting the
presence of well isolated electron excitations within the device. It is
expected that these are associated with long decoherence time and the device
may be suitable for quantum information processing
Longitudinal phase space manipulation in energy recovering linac-driven free-electron lasers
Energy recovering an electron beam after it has participated in a
free-electron laser (FEL) interaction can be quite challenging because of the
substantial FEL-induced energy spread and the energy anti-damping that occurs
during deceleration. In the Jefferson Lab infrared FEL driver-accelerator, such
an energy recovery scheme was implemented by properly matching the longitudinal
phase space throughout the recirculation transport by employing the so-called
energy compression scheme. In the present paper,after presenting a
single-particle dynamics approach of the method used to energy-recover the
electron beam, we report on experimental validation of the method obtained by
measurements of the so-called "compression efficiency" and "momentum
compaction" lattice transfer maps at different locations in the recirculation
transport line. We also compare these measurements with numerical tracking
simulations.Comment: 31 pages, 13 figures, submitted to Phys. Rev. Special Topics A&
Relevance of pseudospin symmetry in proton-nucleus scattering
The manifestation of pseudospin-symmetry in proton-nucleus scattering is
discussed. Constraints on the pseudospin-symmetry violating scattering
amplitude are given which require as input cross section and polarization data,
but no measurements of the spin rotation function. Application of these
constraints to p-58Ni and p-208Pb scattering data in the laboratory energy
range of 200 MeV to 800 MeV, reveals a significant violation of the symmetry at
lower energies and a weak one at higher energies. Using a schematic model
within the Dirac phenomenology, the role of the Coulomb potential in
proton-nucleus scattering with regard to pseudospin symmetry is studied. Our
results indicate that the existence of pseudospin-symmetry in proton-nucleus
scattering is questionable in the whole energy region considered and that the
violation of this symmetry stems from the long range nature of the Coulomb
interaction.Comment: 22 pages including 9 figures, correction of 1 reference, revision of
abstract and major modification of chapter 4, Fig. 6, and Fig. 7; addition of
Fig. 8 and Fig.
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