45 research outputs found
Where are the Uranus Trojans?
The area of stable motion for fictitious Trojan asteroids around Uranus'
equilateral equilibrium points is investigated with respect to the inclination
of the asteroid's orbit to determine the size of the regions and their shape.
For this task we used the results of extensive numerical integrations of orbits
for a grid of initial conditions around the points L4 and L5, and analyzed the
stability of the individual orbits. Our basic dynamical model was the Outer
Solar System (Jupiter, Saturn, Uranus and Neptune). We integrated the equations
of motion of fictitious Trojans in the vicinity of the stable equilibrium
points for selected orbits up to the age of the Solar system of 5 billion
years. One experiment has been undertaken for cuts through the Lagrange points
for fixed values of the inclinations, while the semimajor axes were varied. The
extension of the stable region with respect to the initial semimajor axis lies
between 19.05 < a < 19.3 AU but depends on the initial inclination. In another
run the inclination of the asteroids' orbit was varied in the range 0 < i < 60
and the semimajor axes were fixed. It turned out that only four 'windows' of
stable orbits survive: these are the orbits for the initial inclinations 0 < i
< 7, 9 < i < 13, 31 < i < 36 and 38 < i < 50. We postulate the existence of at
least some Trojans around the Uranus Lagrange points for the stability window
at small and also high inclinations.Comment: 15 pages, 12 figures, submitted to CMD
The orbit of 2010 TK7. Possible regions of stability for other Earth Trojan asteroids
Recently the first Earth Trojan has been observed (Mainzer et al., ApJ 731)
and found to be on an interesting orbit close to the Lagrange point L4 (Connors
et al., Nature 475). In the present study we therefore perform a detailed
investigation on the stability of its orbit and moreover extend the study to
give an idea of the probability to find additional Earth-Trojans. Our results
are derived using different approaches: a) we derive an analytical mapping in
the spatial elliptic restricted three-body problem to find the phase space
structure of the dynamical problem. We explore the stability of the asteroid in
the context of the phase space geometry, including the indirect influence of
the additional planets of our Solar system. b) We use precise numerical methods
to integrate the orbit forward and backward in time in different dynamical
models. Based on a set of 400 clone orbits we derive the probability of capture
and escape of the Earth Trojan asteroids 2010 TK7. c) To this end we perform an
extensive numerical investigation of the stability region of the Earth's
Lagrangian points. We present a detailed parameter study in the regime of
possible stable tadpole and horseshoe orbits of additional Earth-Trojans, i.e.
with respect to the semi-major axes and inclinations of thousands of fictitious
Trojans. All three approaches underline that the Earth Trojan asteroid 2010 TK7
finds himself in an unstable region on the edge of a stable zone; additional
Earth-Trojan asteroids may be found in this regime of stability.Comment: 11 pages, 16 figure
The Resonant Dynamical Evolution of Small Body Orbits Among Giant Planets
Mean motion resonances (MMRs) can lead either to chaotic or regular motion.
We report on a numerical experiment showing that even in one of the most
chaotic regions of the Solar System - the region of the giant planets, there
are numerous bands where MMRs can stabilize orbits of small bodies in a time
span comparable to their lifetimes. Two types of temporary stabilization were
observed: short period ( years) when a body was in a MMR with only
one planet and long period (over years) when a body is located in
overlapping MMRs with two or three planets.
The experiment showed that the Main Belt region can be enriched by cometary
material in its pre-active state due to temporary resonant interactions between
small bodies and giant planets.Comment: 8 pages, 6 figure
Aspects of the planetary Birkhoff normal form
The discovery in [G. Pinzari. PhD thesis. Univ. Roma Tre. 2009], [L.
Chierchia and G. Pinzari, Invent. Math. 2011] of the Birkhoff normal form for
the planetary many--body problem opened new insights and hopes for the
comprehension of the dynamics of this problem. Remarkably, it allowed to give a
{\sl direct} proof of the celebrated Arnold's Theorem [V. I. Arnold. Uspehi
Math. Nauk. 1963] on the stability of planetary motions. In this paper, using a
"ad hoc" set of symplectic variables, we develop an asymptotic formula for this
normal form that may turn to be useful in applications. As an example, we
provide two very simple applications to the three-body problem: we prove a
conjecture by [V. I. Arnold. cit] on the "Kolmogorov set"of this problem and,
using Nehoro{\v{s}}ev Theory [Nehoro{\v{s}}ev. Uspehi Math. Nauk. 1977], we
prove, in the planar case, stability of all planetary actions over
exponentially-long times, provided mean--motion resonances are excluded. We
also briefly discuss perspectives and problems for full generalization of the
results in the paper.Comment: 44 pages. Keywords: Averaging Theory, Birkhoff normal form,
Nehoro{\v{s}}ev Theory, Planetary many--body problem, Arnold's Theorem on the
stability of planetary motions, Properly--degenerate kam Theory, steepness.
Revised version, including Reviewer's comments. Typos correcte
Design and implementation of integrated common mode capacitors for SiC-JFET inverters
Abstract—This paper deals with the issue of electromagnetic interference (EMI) in SiC-JFET inverter power modules, and proposes a solution to limit conducted emissions at high frequencies. SiC-JFET inverters can achieve very fast switching, thereby reducing commutation losses, at the cost of a high level of EMI. In order to limit conducted EMI emissions, it is proposed to integrate small-value common mode (CM) capacitors, directly into the power module. High frequency noise, which is usually difficult to filter, is then contained within the module, thus keeping it far from the external network. This approach is in line with the current trend towards the integration of various functions (such as protection, sensors or drivers) around power devices in modern power modules. To demonstrate this concept, the resulting CM noise was investigated, and compared with a standard configuration. Simulations were used to design the integrated capacitors, and measurements were carried out on an experimental SiC-JFET half-bridge structure. A significant reduction was achieved in the experimentally observed CM conducted emissions, with a very minor influence on the switching waveforms, losses and overall size of the system. The benefits and limitations of this design are discussed, for the case of mid-power range inverters for aircraft applications. Index Terms—Electromagnetic compatibility, Inverters, Multichip modules