3,463 research outputs found
A Dynamical Study of the Non-Star Forming Translucent Molecular Cloud MBM16: Evidence for Shear Driven Turbulence in the Interstellar Medium
We present the results of a velocity correlation study of the high latitude
cloud MBM16 using a fully sampled CO map, supplemented by new CO
data. We find a correlation length of 0.4 pc. This is similar in size to the
formaldehyde clumps described in our previous study. We associate this
correlated motion with coherent structures within the turbulent flow. Such
structures are generated by free shear flows. Their presence in this non-star
forming cloud indicates that kinetic energy is being supplied to the internal
turbulence by an external shear flow. Such large scale driving over long times
is a possible solution to the dissipation problem for molecular cloud
turbulence.Comment: Uses AAS aasms4.sty macros. Accepted for publication in Ap
A perturbative approach to J mixing in f-electron systems: Application to actinide dioxides
We present a perturbative model for crystal-field calculations, which keeps
into account the possible mixing of states labelled by different quantum number
J. Analytical J-mixing results are obtained for a Hamiltonian of cubic symmetry
and used to interpret published experimental data for actinide dioxides. A
unified picture for all the considered compounds is proposed by taking into
account the scaling properties of the crystal-field potential.Comment: 16 pages + 4 figures; will appear http://prb.aps.or
S-mixing and quantum tunneling of the magnetization in molecular nanomagnets
The role of -mixing in the quantum tunneling of the magnetization in
nanomagnets has been investigated. We show that the effect on the tunneling
frequency is huge and that the discrepancy (more than 3 orders of magnitude in
the tunneling frequency) between spectroscopic and relaxation measurements in
Fe can be resolved if -mixing is taken into account.Comment: REVTEX, 10 pages, 3 jpg figures, to appear in PR
Parameterized thermal macromodeling for fast and effective design of electronic components and systems
We present a parameterized macromodeling approach to perform fast and effective dynamic thermal simulations of electronic components and systems where key design parameters vary. A decomposition of the frequency-domain data samples of the thermal impedance matrix is proposed to improve the accuracy of the model and reduce the number of the computationally costly thermal simulations needed to build the macromodel. The methodology is successfully applied to analyze the impact of layout variations on the dynamic thermal behavior of a state-of-the-art 8-finger AlGaN/GaN HEMT grown on a SiC substrate
Enhancement of rare-earth--transition-metal exchange interaction in PrFe probed by inelastic neutron scattering
The fundamental magnetic interactions of PrFe are studied by
inelastic neutron scattering and anisotropy field measurements. Data analysis
confirms the presence of three magnetically inequivalent sites, and reveals an
exceptionally large value of the exchange field. The unexpected importance of
-mixing effects in the description of the ground-state properties of
PrFe is evidenced, and possible applications of related compounds
are envisaged.Comment: 4 RevTeX pages, 4 EPS figures. Accepted for publication by Appl.
Phys. Lett. (will be found at http://apl.aip.org
Magnetic Excitations in NpCoGa5
We report the results of inelastic neutron scattering experiments on
NpCoGa, an isostructural analogue of the PuCoGa superconductor. Two
energy scales characterize the magnetic response in the antiferromagnetic
phase. One is related to a non-dispersive excitation between two crystal field
levels. The other at lower energies corresponds to dispersive fluctuations
emanating from the magnetic zone center. The fluctuations persist in the
paramagnetic phase also, although weaker in intensity. This supports the
possibility that magnetic fluctuations are present in PuCoGa, where
unconventional d-wave superconductivity is achieved in the absence of magnetic
order.Comment: 4 pages, 5 figure
Unexpected phase locking of magnetic fluctuations in the multi-k magnet USb
The spin waves in the multi-k antiferromagnet USb soften and become quasielastic well below the antiferromagnetic ordering temperature TN. This occurs without a magnetic or structural transition. It has been suggested that this change is in fact due to dephasing of the different multi-k components: a switch from 3-k to 1-k behavior. In this work, we use inelastic neutron scattering with tridirectional polarization analysis to probe the quasielastic magnetic excitations and reveal that the 3-k structure does not dephase. More surprisingly, the paramagnetic correlations also maintain the same clear phase correlations well above TN (up to at least 1.4TN)
Model Based Analysis of Shimmy in a Racing Bicycle
In this paper we are presenting a model of a racing bicycle, developed in Modelica language within the Dymola environment. The main purpose is to investigate the dynamic response of the bicycle and its modes of vibration, referring in particular to shimmy. This phenomenon occurs at high speeds and consists of sudden oscillations of the front assembly around the steering axis. Lateral accelerations on the horizontal tube of the frame can reach 5-10 g with a frequency that varies between 5-10 Hz. Even if it is quite uncommon, shimmy is a topic of great relevance, because it may be extremely dangerous for the rider. Thanks to this model, we can show that the main elements which contribute to the rise of the oscillations are the lateral compliance of the frame and the tyres’ deformation
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