1,282 research outputs found
Efficient computation of quasiperiodic oscillations in nonlinear systems with fast rotating parts
We present a numerical method for the investigation of quasiperiodic oscillations in applications modeled by systems of ordinary differential equations. We focus on systems with parts that have a significant rotational speed. An important element of our approach is to change coordinates into a co-rotating frame. We show that this leads to a dramatic reduction of computational effort in the case that gravitational forces can be neglected. As a practical example we study a turbocharger model for which we give a thorough comparison of results for a model with and without gravitational forces
The method of averages applied to the KS differential equations
A new approach for the solution of artificial satellite trajectory problems is proposed. The basic idea is to apply an analytical solution method (the method of averages) to an appropriate formulation of the orbital mechanics equations of motion (the KS-element differential equations). The result is a set of transformed equations of motion that are more amenable to numerical solution
Prediction of huge X-ray Faraday rotation at the Gd N_4,5 threshold
X-ray absorption spectra in a wide energy range around the 4d-4f excitation
threshold of Gd were recorded by total electron yield from in-plane magnetized
Gd metal films. Matching the experimental spectra to tabulated absorption data
reveals unprecedented short light absorption lengths down to 3 nm. The
associated real parts of the refractive index for circularly polarized light
propagating parallel or antiparallel to the Gd magnetization, determined
through the Kramers-Kronig transformation, correspond to a magneto-optical
Faraday rotation of 0.7 degrees per atomic layer. This finding shall allow the
study of magnetic structure and magnetization dynamics of lanthanide elements
in nanosize systems and dilute alloys.Comment: 4 pages, 2 figures, final version resubmitted to Phys. Rev. B, Brief
Reports. Minor change
Temperature-induced reversal of magnetic interlayer exchange coupling
For epitaxial trilayers of the magnetic rare-earth metals Gd and Tb, exchange
coupled through a non-magnetic Y spacer layer, element-specific hysteresis
loops were recorded by the x-ray magneto-optical Kerr effect at the rare-earth
thresholds. This allowed us to quantitatively determine the strength of
interlayer exchange coupling (IEC). In addition to the expected oscillatory
behavior as a function of spacer-layer thickness , a temperature-induced
sign reversal of IEC was observed for constant , arising from
magnetization-dependent electron reflectivities at the magnetic interfaces.Comment: 4 pages, 4 figures; accepted version; minor changes and new Figs. 2
and 4 containing more dat
Fairness perceptions of algorithmic decision-making: A systematic review of the empirical literature
Laws affecting employers of farm labor
"If you hire farm labor, you are responsible for complying with state and federal laws concerned with the safety and well-being of employees."--First page.Stephen F. Matthews, Herman E. Workman, and Patrick B. Starke (Department of Agricultural Economics, College of Agriculture)Revised 3/80/8
Tracking primary thermalization events in graphene with photoemission at extreme timescales
Direct and inverse Auger scattering are amongst the primary processes that
mediate the thermalization of hot carriers in semiconductors. These two
processes involve the annihilation or generation of an electron-hole pair by
exchanging energy with a third carrier, which is either accelerated or
decelerated. Inverse Auger scattering is generally suppressed, as the
decelerated carriers must have excess energies higher than the band gap itself.
In graphene, which is gapless, inverse Auger scattering is instead predicted to
be dominant at the earliest time delays. Here, femtosecond
extreme-ultraviolet pulses are used to detect this imbalance, tracking both the
number of excited electrons and their kinetic energy with time- and
angle-resolved photoemission spectroscopy. Over a time window of approximately
25 fs after absorption of the pump pulse, we observe an increase in conduction
band carrier density and a simultaneous decrease of the average carrier kinetic
energy, revealing that relaxation is in fact dominated by inverse Auger
scattering. Measurements of carrier scattering at extreme timescales by
photoemission will serve as a guide to ultrafast control of electronic
properties in solids for PetaHertz electronics.Comment: 16 pages, 8 figure
X-ray magneto-optics of lanthanide materials: principles and applications
Lanthanide metals are a particular class of magnetic materials in which the
magnetic moments are carried mainly by the localized electrons of the 4f shell.
They are frequently found in technically relevant systems, to achieve, e.g.,
high magnetic anisotropy. Magneto-optical methods in the x-ray range are well
suited to study complex magnetic materials in an element-specific way. In this
work, we report on recent progress on the quantitative determination of
magneto-optical constants of several lanthanides in the soft x-ray region and
we show some examples of applications of magneto-optics to hard-magnetic
interfaces and exchange-coupled layered structures containing lanthanide
elements.Comment: 7 pages, 6 figures, invited contribution to the Symposium "X-ray
magneto-optics" of the Spring Meeting of the German Physical Society held in
Regensburg, Germany, 8-12 March 2004. Revised version, minor change
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