7,444 research outputs found
Variations in elemental composition of several MEV/nucleon ions observed in interplanetary space
Six years of accumulated ISEE-3 and IMP-8 data to study variations in elemental relative abundances among the different populations of energetic ions seen in interplanetary space are surveyed. Evidence suggesting that heavy ion enrichments may be organized by a rigidity scaling factor A/Z over the range H to Fe is presented. Data to support the hypothesis that shock-associated particles are probably accelerated from ambient energetic fluxes are shown
The Penguin: a Low Reynolds Number Powered Glider for Station Keeping Missions
The Penguin is a low Reynolds number (approx. 100,000) remotely piloted vehicle (RPV). It was designed to fly three laps indoors around two pylons in a figure-eight course while maximizing loiter time. The Penguin's low Reynolds number mission is an important one currently being studied for possible future flights in the atmospheres of other planets and for specialized military missions. Although the Penguin's mission seemed quite simple at first, the challenges of such low Reynolds number flight have proven to be quite unique. In addition to the constraint of low Reynolds number flight, the aircraft had to be robust in its control, highly durable, and it had to carry a small instrument package. The Penguin's flight plan, concept, performance, aerodynamic design, weight estimation, structural design, propulsion, stability and control, and cost estimate is detailed
Quasi-one-dimensional Bose gases with large scattering length
Bose gases confined in highly-elongated harmonic traps are investigated over
a wide range of interaction strengths using quantum Monte Carlo techniques. We
find that the properties of a Bose gas under tight transverse confinement are
well reproduced by a 1d model Hamiltonian with contact interactions. We point
out the existence of a unitary regime, where the properties of the quasi-1d
Bose gas become independent of the actual value of the 3d scattering length. In
this unitary regime, the energy of the system is well described by a hard rod
equation of state. We investigate the stability of quasi-1d Bose gases with
positive and negative 3d scattering length.Comment: 5 pages, 3 figure
On the role of shake-off in single-photon double ionization
The role of shake-off for double ionization of atoms by a single photon with
finite energy has become the subject of debate. In this letter, we attempt to
clarify the meaning of shake-off at low photon energies by comparing different
formulations appearing in the literature and by suggesting a working
definition. Moreover, we elaborate on the foundation and justification of a
mixed quantum-classical ansatz for the calculation of single-photon double
ionization
Anisotropic thermal expansion of Fe1.06Te and FeTe0.5Se0.5 single crystals
Heat capacity and anisotropic thermal expansion was measured for Fe1.06Te and
FeTe0.5Se0.5 single crystals. Previously reported phase transitions are clearly
seen in both measurements. In both cases the thermal expansion is anisotropic.
The uniaxial pressure derivatives of the superconducting transition temperature
in FeTe0.5Se0.5 inferred from the Ehrenfest relation have opposite signs for
in-plane and c-axis pressures. Whereas the Gruneisen parameters for both
materials are similar and only weakly temperature-dependent above ~ 80 K, at
low temperatures (in the magnetically ordered phase) the magnetic contribution
to the Gruneisen parameter in Fe1.06Te is significantly larger than electron
and phonon contributions combined
- …