5,882 research outputs found
The Fundamentals of Radar with Applications to Autonomous Vehicles
Radar systems can be extremely useful for applications in autonomous vehicles. This paper seeks to show how radar systems function and how they can apply to improve autonomous vehicles. First, the basics of radar systems are presented to introduce the basic terminology involved with radar. Then, the topic of phased arrays is presented because of their application to autonomous vehicles. The topic of digital signal processing is also discussed because of its importance for all modern radar systems. Finally, examples of radar systems based on the presented knowledge are discussed to illustrate the effectiveness of radar systems in autonomous vehicles
De Sitter Vacua from a D-term Generated Racetrack Uplift
We propose an uplift mechanism using a structure of multi-K\"ahler moduli
dependence in the F-term potential of type IIB string theory compactifications.
This mechanism requires a D-term condition that fixes one modulus to be
proportional to another modulus, resulting in a trivial D-term potential. De
Sitter minima are realized along with an enhancement of the volume in the Large
Volume Scenario and no additional suppression of the uplift term such as
warping is required. We further show the possibility to realize the uplift
mechanism in the presence of more K\"ahler moduli such that we expect the
uplift mechanism to work in many other compactifications.Comment: 20 pages, 1 figur
Nuclear quantum transport for barrier problems
A method is presented which allows one to introduce collective coordinates
self-consistently, in distinction to the Caldeira-Leggett model. It is
demonstrated how the partition function Z for the total nuclear system can be
calculated to deduce information both on its level density as well as on the
decay rate of unstable modes. For the evaluation of Z different approximations
are discussed. A recently developed variational approach turns out superior to
the conventional methods that include quantum effects on the level of local
RPA. Dissipation is taken into account by applying energy smearing, simulating
in this way the coupling to more complicated states. In principle, such a
coupling must depend on temperature. Previous calculations along another
microscopic approach show this fact to imply an intriguing variation of the
transport coefficients of collective motion with T. The relevance of this
feature is demonstrated for the thermal fission rate and for the formation
probability of super-heavy elements.Comment: 8 pages, 4 figures, presented at FUSION03, Matsushima, Miyagi, Japan,
Nov 12-15, 2003, to appear in Progress of Theoretical Physic
The partition function of an interacting many body system: beyond the perturbed static path approximation
Based on the path integral representation of the partition function of a many
body system with separable two body interaction we propose a systematic
extension of the perturbed static path approximation (PSPA) to lower
temperatures. Thereby, special attention must be paid to instabilities of the
classical mean field solution in functional space that cause divergencies
within the conventional PSPA. As a result we develop an approximation
applicable from high to very low temperatures. These findings are tested
against exact results for the archetypical cases of a particle moving in a one
dimensional double well and the exactly solvable Lipkin model. In particular,
we obtain a very good approximation to the level density of the Lipkin model
even at low thermal excitations. Our results may have potential applications in
low temperature nuclear physics and mesoscopic systems, e.g. for gap
fluctuations in nanoscale superconducting devices previously studied within a
PSPA type of approximation.
PACS: 5.30.-d, 24.60.-k, 21.10.Ma, 74.25.BtComment: 11 pages, 7 figures, replaced with shortened version accepted for
publication in EPJB, minor changes not affecting any result
CELSS science needs
Questions and areas of study that need to be persued in order to develope a Controlled Ecological Life Support System are posed. Research topics needing attention are grouped under various leadings: ecology, genetics, plant pathology, cybernetics, chemistry, computer science, fluid dynamics, optics, and solid-state physics
Damped collective motion of many body systems: A variational approach to the quantal decay rate
We address the problem of collective motion across a barrier like encountered
in fission. A formula for the quantal decay rate is derived which bases on a
recently developed variational approach for functional integrals. This formula
can be applied to low temperatures that have not been accessible within the
former PSPA type approach. To account for damping of collective motion one
particle Green functions are dressed with appropriate self-energies.Comment: revised version, submitted to Nuclear Physics A, 20 pages, 2 figure
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