12,107 research outputs found
Continuum Deformation of a Multiple Quadcopter Payload Delivery Team without Inter-Agent Communication
This paper proposes continuum deformation as a strategy for controlling the
collective motion of a multiple quadcopter system (MQS) carrying a common
payload. Continuum deformation allows expansion and contraction of inter-agent
distances in a 2D motion plane to follow desired motions of three team leaders.
The remaining quadcopter followers establish the desired continuum deformation
only by knowing leaders positions at desired sample time waypoints without the
need for inter-agent communication over the intermediate intervals. Each
quadcopter applies a linear-quadratic-Gaussian (LQG) controller to track the
desired trajectory given by the continuum deformation in the presence of
disturbance and measurement noise. Results of simulated cooperative aerial
payload transport in the presence of uncertainty illustrate the application of
continuum deformation for coordinated transport through a narrow channel
Brane world models need low string scale
Models with large extra dimensions offer the possibility of the Planck scale being of order the electroweak scale, thus alleviating the gauge hierarchy problem. We show that these models suffer from a breakdown of unitarity at around three quarters of the low effective Planck scale. An obvious candidate to fix the unitarity problem is string theory. We therefore argue that it is necessary for the string scale to appear below the effective Planck scale and that the first signature of such models would be string resonances. We further translate experimental bounds on the string scale into bounds on the effective Planck scale
Classical Robustness of Quantum Unravellings
We introduce three measures which quantify the degree to which quantum
systems possess the robustness exhibited by classical systems when subjected to
continuous observation. Using these we show that for a fixed environmental
interaction the level of robustness depends on the measurement strategy, or
unravelling, and that no single strategy is maximally robust in all ways.Comment: 8 Pages, 2 figures, Version 2. Minor changes to wording for
clarification and some references added. Accepted for publication in
Europhysics Letter
Hydrogen-Related Conversion Processes of Ge-Related Point Defects in Silica Triggered by UV Laser Irradiation
The conversion processes of Ge-related point defects triggered in amorphous
SiO2 by 4.7eV laser exposure were investigated. Our study has focused on the
interplay between the (=Ge•-H) H(II) center and the twofold coordinated
Ge defect (=Ge••). The former is generated in the post-irradiation
stage, while the latter decays both during and after exposure. The
post-irradiation decay kinetics of =Ge•• is isolated and found to
be anti-correlated to the growth of H(II), at least at short times. From this
finding it is suggested that both processes are due to trapping of radiolytic
H0 at the diamagnetic defect site. Furthermore, the anti-correlated behavior is
preserved also under repeated irradiation: light at 4.7eV destroys the already
formed H(II) centers and restore their precursors =Ge••. This
process leads to repeatability of the post-irradiation kinetics of the two
species after multiple laser exposures. A comprehensive scheme of chemical
reactions explaining the observed post-irradiation processes is proposed and
tested against experimental data.Comment: 25 pages, 7 figures, submitted to Phys. Rev.
Analysis of Current and Potential Treatments for Chronic Lymphocytic Leukemia
Chronic Lymphocytic Leukemia (CLL) is one of the most common forms of adult leukemia in North Americans. However, it has been shown through the analysis of clinical studies and synopses of medical research that no current treatment indefinitely cures CLL or prolongs the life of CLL patients. Current CLL therapies are either symptomatic treatments (chemotherapy and immunotherapy) that do not improve complete remission rates or effective treatments that target the actual cancer but have excessive morbidity and toxicity rates (stem cell transplants). Conventional CLL treatments are inadequate according to the results of clinical trials and research of field experts. Potential fields of research (nanotechnology, gene therapy and phytotherapy) that show promise as CLL therapies according to the studies of researchers and scientists should be further examined. If a cure for CLL is to be found, the focus of treatment needs to move away from symptomatic relief toward the identification and remedy of the cause of the cancer
Hearts Torn Asunder: Trauma in the Civil War’s Final Campaign in North Carolina
In Hearts Torn Asunder: Trauma in the Civil War’s Final Campaign in North Carolina, author Earnest A. Dollar focuses...on the war\u27s impact on the soldiers and on the civilians caught between the two armies in a fresh look at...the war\u27s most significant remaining theater after Appomattox writes reviewer Jonathan M. Atkin
Non-locality in quantum field theory due to general relativity
We show that general relativity coupled to a quantum field theory generically leads to non-local effects in the matter sector. These non-local effects can be described by non-local higher dimensional operators which remarkably have an approximate shift symmetry. When applied to inflationary models, our results imply that small non-Gaussianities are a generic feature of models based on general relativity coupled to matter fields. However, these effects are too small to be observable in the cosmic microwave background
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