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Rapid Prototyping of Functional Three-Dimensional Microsolenoids and Electromagnets by High-Pressure Laser Chemical Vapor Deposition
Three-dimensional laser chemical vapor deposition (3D-LCVD) is an emerging process
which bridges the gap between various macro-scale rapid prototyping (RP) systems and microfabrication technologies. With the ability to deposit both metals and dielectrics 3D-LCVD
may be used to prototype integrated electromechanical components from sub-micron to centimeter scales. This technological niche is increasingly important with the ever-decreasing size
and sophistication of consumer and industrial products.
The objective of this work was the development of functional microsolenoids and electromagnets, using 3D-LCVD as the primary fabrication tool. High-aspect-ratio microsolenoids
have the potential to generate much greater magnetic-field densities than their thin-film counterparts,l and have many advantages when used as actuators in microelectromechanical systems (MEMS).2 3D-LCVD provides a means of fabricating such helical structures, with an
ease unparalleled by any lithographic or rapid prototyping process.Mechanical Engineerin
Nonlinear wave interaction and spin models in the MHD regime
Here we consider the influence on the electron spin in the MHD regime.
Recently developed models which include spin-velocity correlations are taken as
a starting point. A theoretical argument is presented, suggesting that in the
MHD regime a single fluid electron model with spin correlations is equivalent
to a model with spin-up and spin-down electrons constituting different fluids,
but where the spin-velocity correlations are omitted. Three wave interaction of
2 shear Alfven waves and a compressional Alfven wave is then taken as a model
problem to evaluate the asserted equivalence. The theoretical argument turns
out to be supported, as the predictions of the two models agree completely.
Furthermore, the three wave coupling coefficients obey the Manley-Rowe
relations, which give further support to the soundness of the models and the
validity of the assumptions made in the derivation. Finally we point out that
the proposed two-fluid model can be incorporated in standard Particle-In-Cell
schemes with only minor modifications.Comment: 8 page
Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710
Aims. The observation of gamma -ray flares from blazar 0836+710 in 2011,
following a period of quiescence, offered an opportunity to study correlated
activity at different wavelengths for a high-redshift (z=2.218) active galactic
nucleus. Methods. Optical and radio monitoring, plus Fermi-LAT gamma-ray
monitoring provided 2008-2012 coverage, while Swift offered auxiliary optical,
ultraviolet, and X-ray information. Other contemporaneous observations were
used to construct a broad-band spectral energy distribution. Results. There is
evidence of correlation but not a measurable lag between the optical and
gamma-ray flaring emission. On the contrary, there is no clear correlation
between radio and gamma-ray activity, indicating radio emission regions that
are unrelated to the parts of the jet that produce the gamma-rays. The
gamma-ray energy spectrum is unusual in showing a change of shape from a power
law to a curved spectrum when going from the quiescent state to the active
state.Comment: 11 pages, 10 figures, Accepted for publication in A&
The Molecular Line Opacity of MgH in Cool Stellar Atmospheres
A new, complete, theoretical rotational and vibrational line list for the A-X
electronic transition in MgH is presented. The list includes transition
energies and oscillator strengths for all possible allowed transitions and was
computed using the best available theoretical potential energies and dipole
transition moment function with the former adjusted to account for experimental
data. The A-X line list, as well as new line lists for the B'-X and the X-X
(pure rovibrational) transitions, were included in comprehensive stellar
atmosphere models for M, L, and T dwarfs and solar-type stars. The resulting
spectra, when compared to models lacking MgH, show that MgH provides
significant opacity in the visible between 4400 and 5600 Angstrom. Further,
comparison of the spectra obtained with the current line list to spectra
obtained using the line list constructed by Kurucz (1993) show that the Kurucz
list significantly overestimates the opacity due to MgH particularly for the
bands near 5150 and 4800 Angstrom with the discrepancy increasing with
decreasing effective temperature.Comment: 10 pages, 4 figures, 3 table
Ternary q-Virasoro-Witt Hom-Nambu-Lie algebras
In this paper we construct ternary -Virasoro-Witt algebras which
-deform the ternary Virasoro-Witt algebras constructed by Curtright, Fairlie
and Zachos using enveloping algebra techniques. The ternary
Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos depend on a
parameter and are not Nambu-Lie algebras for all but finitely many values of
this parameter. For the parameter values for which the ternary Virasoro-Witt
algebras are Nambu-Lie, the corresponding ternary -Virasoro-Witt algebras
constructed in this article are also Hom-Nambu-Lie because they are obtained
from the ternary Nambu-Lie algebras using the composition method. For other
parameter values this composition method does not yield Hom-Nambu Lie algebra
structure for -Virasoro-Witt algebras. We show however, using a different
construction, that the ternary Virasoro-Witt algebras of Curtright, Fairlie and
Zachos, as well as the general ternary -Virasoro-Witt algebras we construct,
carry a structure of ternary Hom-Nambu-Lie algebra for all values of the
involved parameters
The new 150 MVAr, 18 kV static var compensator for SPS: background, design and commissioning
A new Static Var Compensator (SVC) was designed, installed and commissioned by ABB for CERNâs Super Proton Synchrotron (SPS) accelerator. Due to the sensitive nature of the pulsating power converter load for the SPS magnets, very strict requirements were imposed on the stabilisation of the 18 kV bus voltage and its harmonic distortion. The adopted solution comprises a 150 Mvar TCR and eight harmonic filters with a total power of 130 Mvar. The paper gives a detailed description of the project background, system design and SVC installation. Finally, the results of the SVC performance tests are presented
The Dynamics of Radiative Shock Waves: Linear and Nonlinear Evolution
The stability properties of one-dimensional radiative shocks with a power-law
cooling function of the form are the main
subject of this work. The linear analysis originally presented by Chevalier &
Imamura, is thoroughfully reviewed for several values of the cooling index
and higher overtone modes. Consistently with previous results, it is
shown that the spectrum of the linear operator consists in a series of modes
with increasing oscillation frequency. For each mode a critical value of the
cooling index, , can be defined so that modes with are unstable, while modes with
are stable. The perturbative analysis is complemented by several numerical
simulations to follow the time-dependent evolution of the system for different
values of . Particular attention is given to the comparison between
numerical and analytical results (during the early phases of the evolution) and
to the role played by different boundary conditions. It is shown that an
appropriate treatment of the lower boundary yields results that closely follow
the predicted linear behavior. During the nonlinear regime, the shock
oscillations saturate at a finite amplitude and tend to a quasi-periodic cycle.
The modes of oscillations during this phase do not necessarily coincide with
those predicted by linear theory, but may be accounted for by mode-mode
coupling.Comment: 33 pages, 12 figures, accepted for publication on the Astrophysical
Journa
Suzaku observations of Markarian 335: evidence for a distributed reflector
We report on a 151 ks net exposure Suzaku observation of the Narrow Line
Seyfert 1 galaxy Mrk 335. The 0.5-40 keV spectrum contains a broad Fe line, a
strong soft excess below about 2 keV and a Compton hump around 20-30 keV. We
find that a model consisting of a power law and two reflectors provides the
best fit to the time-averaged spectrum. In this model, an ionized, heavily
blurred, inner reflector produces most of the soft excess, while an almost
neutral outer reflector (outside ~40 r_g) produces most of the Fe line
emission. The spectral variability of the observation is characterised by
spectral hardening at very low count rates. In terms of our power-law +
two-reflector model it seems like this hardening is mainly caused by pivoting
of the power law. The rms spectrum of the entire observation has the curved
shape commonly observed in AGN, although the shape is significantly flatter
when an interval which does not contain any deep dip in the lightcurve is
considered. We also examine a previous 133 ks XMM-Newton observation of Mrk
335. We find that the XMM-Newton spectrum can be fitted with a similar
two-reflector model as the Suzaku data and we confirm that the rms spectrum of
the observation is flat. The flat rms spectra, as well as the high-energy data
from the Suzaku PIN detector, disfavour an absorption origin for the soft
excess in Mrk 335.Comment: 13 pages, 13 figures. Accepted for publication in MNRA
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