36,511 research outputs found
Bifurcation Boundary Conditions for Switching DC-DC Converters Under Constant On-Time Control
Sampled-data analysis and harmonic balance analysis are applied to analyze
switching DC-DC converters under constant on-time control. Design-oriented
boundary conditions for the period-doubling bifurcation and the saddle-node
bifurcation are derived. The required ramp slope to avoid the bifurcations and
the assigned pole locations associated with the ramp are also derived. The
derived boundary conditions are more general and accurate than those recently
obtained. Those recently obtained boundary conditions become special cases
under the general modeling approach presented in this paper. Different analyses
give different perspectives on the system dynamics and complement each other.
Under the sampled-data analysis, the boundary conditions are expressed in terms
of signal slopes and the ramp slope. Under the harmonic balance analysis, the
boundary conditions are expressed in terms of signal harmonics. The derived
boundary conditions are useful for a designer to design a converter to avoid
the occurrence of the period-doubling bifurcation and the saddle-node
bifurcation.Comment: Submitted to International Journal of Circuit Theory and Applications
on August 10, 2011; Manuscript ID: CTA-11-016
A high flux source of cold strontium atoms
We describe an experimental apparatus capable of achieving a high loading
rate of strontium atoms in a magneto-optical trap operating in a high vacuum
environment. A key innovation of this setup is a two dimensional
magneto-optical trap deflector located after a Zeeman slower. We find a loading
rate of 6x10^9/s whereas the lifetime of the magnetically trapped atoms in the
3P2 state is 54s.Comment: 12 pages, 16 figure
Non-Gaussian features from the inverse volume corrections in loop quantum cosmology
In this paper we study the non-Gaussian features of the primordial
fluctuations in loop quantum cosmology with the inverse volume corrections. The
detailed analysis is performed in the single field slow-roll inflationary
models. However, our results reflect the universal characteristics of
bispectrum in loop quantum cosmology. The main corrections to the scalar
bispectrum come from two aspects: one is the modifications to the standard
Bunch-Davies vacuum, the other is the corrections to the background dependent
variables, such as slow-roll parameters. Our calculations show that the loop
quantum corrections make of the inflationary models increase
0.1%. Moreover, we find that two new shapes arise, namely and
. The former gives a unique loop quantum feature which is less
correlated with the local, equilateral and single types, while the latter is
highly correlated with the local one.Comment: matched to the published version. 30 pages, 4 figure
Orbital-selective Mott transitions in the degenerate Hubbard model
We investigate the Mott transitions in two-band Hubbard models with different
bandwidths. Applying dynamical mean field theory, we discuss the stability of
itinerant quasi-particle states in each band. We demonstrate that separate Mott
transitions occur at different Coulomb interaction strengths in general, which
merge to a single transition only under special conditions. This kind of
behavior may be relevant for the physics of the single-layer ruthenates,
CaSrRuO.Comment: 4 pages, 4 figure
Electromagnetic Interaction of Massive Spin-3 State from String Theory
In the given work we study an interaction of second massive state of an open
boson string with the constant electromagnetic field. This state contains
massive fields with spins 3 and 1. Using the method of an open string BRST
quantization, we receive gauge-invariant lagrangian, describing the
electromagnetic interaction of these fields. From the explicit view of
transformations and lagrangian it follows that the presence of external
constant e/m field leads to the mixing of the given level states. Most likely
that the presence of the external field will lead to the mixing of the states
at other mass string levels as well.Comment: 17 pages, LaTeX, no figure
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