7,201 research outputs found
Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas
Electron heating and ionization dynamics in capacitively coupled radio
frequency (RF) atmospheric pressure microplasmas operated in helium are
investigated by Particle in Cell simulations and semi-analytical modeling. A
strong heating of electrons and ionization in the plasma bulk due to high bulk
electric fields are observed at distinct times within the RF period. Based on
the model the electric field is identified to be a drift field caused by a low
electrical conductivity due to the high electron-neutral collision frequency at
atmospheric pressure. Thus, the ionization is mainly caused by ohmic heating in
this "Omega-mode". The phase of strongest bulk electric field and ionization is
affected by the driving voltage amplitude. At high amplitudes, the plasma
density is high, so that the sheath impedance is comparable to the bulk
resistance. Thus, voltage and current are about 45{\deg} out of phase and
maximum ionization is observed during sheath expansion with local maxima at the
sheath edges. At low driving voltages, the plasma density is low and the
discharge becomes more resistive resulting in a smaller phase shift of about
4{\deg}. Thus, maximum ionization occurs later within the RF period with a
maximum in the discharge center. Significant analogies to electronegative low
pressure macroscopic discharges operated in the Drift-Ambipolar mode are found,
where similar mechanisms induced by a high electronegativity instead of a high
collision frequency have been identified
A low power clock generator with adaptive inter-phase charge balancing for variability compensation in 40-nm CMOS
Power dissipation besides chip area is still one main optimization issue
in high performance CMOS design. Regarding high throughput building blocks
for digital signal processing architectures
which are optimized down to the physical
level a complementary two-phase clocking scheme (CTPC) is often
advantageous concerning ATE-efficiency.
The clock
system dissipates a significant part of overall power up to more than 50%
in some applications.
<br><br>
One efficient power saving strategy for
CTPC signal generation is the charge balancing technique.
To achieve high efficiency with this approach
a careful optimization of timing relations within the control
is inevitable.
<br><br>
However, as in modern CMOS processes device variations
increase,
timing relations between
sensitive control signals
can be affected seriously.
In order to compensate for the influence of global and local variations in this
work, an adaptive control system for charge balancing in a CTPC generator
is presented. An adjustment for the degree of charge recycling is performed
in each clock cycle.
In the case of insufficient recycling
the delay elements which define duration and timing position of
the recycling pulse are corrected by switchable timing units.
<br><br>
In a benchmark with the conventional clock generation system,
a power reduction gain
of up to 24.7% could be achieved. This means saving in power
of more than 12% for a complete number-crunching building block
Maximal multihomogeneity of algebraic hypersurface singularities
From the degree zero part of logarithmic vector fields along an algebraic
hypersurface singularity we indentify the maximal multihomogeneity of a
defining equation in form of a maximal algebraic torus in the embedded
automorphism group. We show that all such maximal tori are conjugate and in
one-to-one correspondence to maxmimal tori in the degree zero jet of the
embedded automorphism group.
The result is motivated by Kyoji Saito's characterization of quasihomogeneity
for isolated hypersurface singularities and extends its formal version and a
result of Hauser and Mueller.Comment: 5 page
Resonant electron heating and molecular phonon cooling in single C junctions
We study heating and heat dissipation of a single \c60 molecule in the
junction of a scanning tunneling microscope (STM) by measuring the electron
current required to thermally decompose the fullerene cage. The power for
decomposition varies with electron energy and reflects the molecular resonance
structure. When the STM tip contacts the fullerene the molecule can sustain
much larger currents. Transport simulations explain these effects by molecular
heating due to resonant electron-phonon coupling and molecular cooling by
vibrational decay into the tip upon contact formation.Comment: Accepted in Phys. Rev. Let
Scalar correlations in a quark plasma and low mass dilepton production
We investigate possible consequences of resonant scalar interactions for
dilepton production from a quark plasma at the chiral phase transition. It is
found that this production mechanism is strongly suppressed compared to the
Born process and has no significance for present experiments.Comment: 7 pages revtex, 2 ps figure
North Atlantic 2001 - Part 3 Cruise No. 50, Leg 3 20 June – 15 July 2001, St. John’s – Reykjavik J. Holfort,
Personalized smart environments to increase inclusion of people with Down's Syndrome
Most people with Downs Syndrome (DS) experience low integration with society. Recent research and new opportunities for their integration in mainstream education and work provided numerous cases where levels of achievement exceeded the (limiting) expectations. This paper describes a project, POSEIDON, aiming at developing a technological infrastructure which can foster a growing number of services developed to support people with DS. People with DS have their own strengths, preferences and needs so POSEIDON will focus on using their strengths to provide support for their needs whilst allowing each individual to personalize the solution based on their preferences. This project is user-centred from its inception and will give all main stakeholders ample opportunities to shape the output of the project, which will ensure a final outcome which is of practical usefulness and interest to the intended users
The orbit rigidity matrix of a symmetric framework
A number of recent papers have studied when symmetry causes frameworks on a
graph to become infinitesimally flexible, or stressed, and when it has no
impact. A number of other recent papers have studied special classes of
frameworks on generically rigid graphs which are finite mechanisms. Here we
introduce a new tool, the orbit matrix, which connects these two areas and
provides a matrix representation for fully symmetric infinitesimal flexes, and
fully symmetric stresses of symmetric frameworks. The orbit matrix is a true
analog of the standard rigidity matrix for general frameworks, and its analysis
gives important insights into questions about the flexibility and rigidity of
classes of symmetric frameworks, in all dimensions.
With this narrower focus on fully symmetric infinitesimal motions, comes the
power to predict symmetry-preserving finite mechanisms - giving a simplified
analysis which covers a wide range of the known mechanisms, and generalizes the
classes of known mechanisms. This initial exploration of the properties of the
orbit matrix also opens up a number of new questions and possible extensions of
the previous results, including transfer of symmetry based results from
Euclidean space to spherical, hyperbolic, and some other metrics with shared
symmetry groups and underlying projective geometry.Comment: 41 pages, 12 figure
489 ANAPHYLATOXINE RECEPTORS AND COMPLEMENT REGULATORY PROTEINS IN TENDON: INTERRELATION WITH IMMUNOREGULATORY CYTOKINES
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