401,282 research outputs found
Identification of left ventricular model parameters
Simulations with a model of left ventricular pressure generation consisting of time-varying elastance, resistance, series-elastance, and deactivation were fitted to pressure curves measured in the isolated rabbit ventricle. For constant ejection flows, a fit with a RMS error of 2.78 mmHg was obtained provided that deactivation was actually incorporated in the model. Deactivation was assumed to depend linearly on end ejection pressure. Resistance was found to be independent of volum
Galactic longitude dependent Galactic model parameters
We present the Galactic model parameters for thin disc estimated by Sloan
Digital Sky Survey (SDSS) data of 14 940 stars with apparent magnitudes
in six intermediate latitude fields in the first Galactic
quadrant. Star/galaxy separation was performed by using the photometric
pipeline and the isodensity contours in the two colour
diagram. The separation of thin disc stars is carried out by the bimodal
distribution of stars in the histogram, and the absolute magnitudes
were evaluated by a procedure presented in the literature Bilir et al. (2005).
Exponential density law fits better to the derived density functions for the
absolute magnitude intervals and , whereas
sech/sech laws are more appropriate for absolute magnitude intervals
and . We showed that the scaleheight and
scalelength are Galactic longitude dependent. The average values and ranges of
the scaleheight and the scalelength are pc ( pc)
and pc ( pc) respectively. This result would
be useful to explain different numerical values claimed for those parameters
obtained by different authors for the fields in different directions of the
Galaxy.Comment: 28 pages, including 12 figures and 7 tables, accepted for publication
in New Astronom
Volume limited dependent Galactic model parameters
We estimated 34 sets of Galactic model parameters for three intermediate
latitude fields with Galactic longitudes l=60, l=90, and l=180, and we
discussed their dependence on the volume. Also, we confirmed the variation of
these parameters with absolute magnitude and Galactic longitude. The star
samples in two fields are restricted with bright and unit absolute magnitude
intervals, (4,5], and (5,6], whereas for the third field a larger absolute
magnitude interval is adopted, (4,10]. The limiting apparent magnitudes of star
samples are g=15 and g=22.5 mag which provide space densities within distances
in the line of sight 0.9 and 25 kpc. The Galactic model parameters for the thin
disc are not volume dependent. However, the ones for thick disc and halo do
show spectacular trends in their variations with volume, except for the
scalelength of the thick disc. The local space density of the thick disc
increases, whereas the scaleheight of the same Galactic component decreases
monotonically. However, both model parameters approach asymptotic values at
large distances. The axial ratio of the halo increases abruptly for the volumes
where thick disc is dominant, whereas it approaches an asymptotic value
gradually for larger volumes, indicating a continuous transition from disclike
structure to a spherical one at the outermost region of the Galaxy. The
variation of the Galactic model parameters with absolute magnitude can be
explained by their dependence on the stellar luminosity, whereas the variation
with volume and Galactic longitude at short distances is a bias in analysis.Comment: 12 pages, including 8 figures and 5 tables, accepted for publication
in PAS
Projecting Ising Model Parameters for Fast Mixing
Inference in general Ising models is difficult, due to high treewidth making
tree-based algorithms intractable. Moreover, when interactions are strong,
Gibbs sampling may take exponential time to converge to the stationary
distribution. We present an algorithm to project Ising model parameters onto a
parameter set that is guaranteed to be fast mixing, under several divergences.
We find that Gibbs sampling using the projected parameters is more accurate
than with the original parameters when interaction strengths are strong and
when limited time is available for sampling.Comment: Advances in Neural Information Processing Systems 201
Standard Model Parameters and the Cosmological Constant
Simple functional relations amongst standard model couplings, including
gravitional, are conjectured. Possible implications for cosmology and future
theory are discussed.Comment: submitted to Physical Review
The experimental determination of tyre model parameters
SUMMARY
This report describes the analysis of a series of experiments on pneumatic tyres
which were designed to test the various hypotheses: regarding the deformed shape of a
tyre during the steering process.
The experiments consisted of several separate tests first described in Ref. 1 and 2.
a) The application of a point lateral force or a moment at one position on the tread band
which is restrained at the centre of the wheel, and the measurement of the resulting
lateral deflection of each point of the tyre perimeter.
b) The application of a uniform force around the tyre perimeter on a hollow cylindrical
former and applying a load at the centre of the wheel.
c) Direct determination of tread band tension by cutting the tread band and bridging the
cut by a dynamometer.
d) Estimation of the bending modulus of the tread band by test on sections cut from the
tread band.
The analysis of the experiments is carried out by first transforming the test results
into a Fourier series and determining the spectral content of the bending line with an
harmonic analysis. Transfer functions of beam and string models are derived and applied
to the test results. A method of considering a three parameter model is described
Trying to understand the Standard Model parameters
We stress the importance of the circa 20 parameters in the Standard Model,
which are not fixed by the model but only determined experimentally, as a
window to the physics beyond the Standard Model. However, it is a tiny window
in as far as these numbers contain only the information corresponding to about
one line of text. Looking for a method to study these coupling and mass
parameters, we put forward the idea of the Multiple Point Principle as a first
step. This principle states that Nature adjusts the coupling and mass
parameters so as to make many different vacuum states exist and have
approximately the same energy densities (cosmological constants). As an
illustrative application, we put up the proposal that a small increase (maybe
only an infinitesimal one) in the value of the top quark coupling constant
could lead to a new vacuum phase; in this new phase the binding of a bound
state of 6 top quarks and 6 anti-top quarks becomes so strong as to become a
tachyon and condense in the vacuum. Assuming the existence of a third
degenerate vacuum at the fundamental energy scale, we present a solution to the
hierarchy problem of why the ratio of the fundamental scale to the electroweak
scale is so large. We also present a 5 parameter fit to the orders of magnitude
of the quark-lepton masses and mixing angles in the Family Replicated Gauge
Group Model. In this model, the Standard Model gauge group and a gauged B-L
(baryon number minus lepton number) is extended to one set of gauge fields for
each family of fermions.Comment: Institute address corrected and one reference adde
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