13,929 research outputs found
Nonlinear projective filtering I: Background in chaos theory
We derive a locally projective noise reduction scheme for nonlinear time
series using concepts from deterministic dynamical systems, or chaos theory. We
will demonstrate its effectiveness with an example with known deterministic
dynamics and discuss methods for the verification of the results in the case of
an unknown deterministic system.Comment: 4 pages, PS figures, needs nolta.st
Nonlinear projective filtering I: Application to real time series
We discuss applications of nonlinear filtering of time series by locally
linear phase space projections. Noise can be reduced whenever the error due to
the manifold approximation is smaller than the noise in the system. Examples
include the real time extraction of the fetal electrocardiogram from abdominal
recordings.Comment: 4 pages, PS figures, needs nolta.st
SIMDET - Version 4 A Parametric Monte Carlo for a TESLA Detector
A new release of the parametric detector Monte Carlo program \verb+SIMDET+
(version 4.01) is now available. We describe the principles of operation and
the usage of this program to simulate the response of a detector for the TESLA
linear collider. The detector components are implemented according to the TESLA
Technical Design Report. All detector component responses are treated in a
realistic way using a parametrisation of results from the {\em ab initio} Monte
Carlo program \verb+BRAHMS+. Pattern recognition is emulated using a complete
cross reference between generated particles and detector response. Also, for
charged particles, the covariance matrix and information are made
available. An idealised energy flow algorithm defines the output of the
program, consisting of particles generically classified as electrons, photons,
muons, charged and neutral hadrons as well as unresolved clusters. The program
parameters adjustable by the user are described in detail. User hooks inside
the program and the output data structure are documented.Comment: 30 pages, 7 figure
Experimental investigation of the performance of a supersonic compressor cascade
Results are presented from an experimental investigation of a linear, supersonic, compressor cascade tested in the supersonic cascade wind tunnel facility at the DFVLR in Cologne, Federal Republic of Germany. The cascade design was derived from the near-tip section of a high-through-flow axial flow compressor rotor with a design relative inlet Mach number of 1.61. Test data were obtained over a range of inlet Mach numbers from 1.23 to 1.71, and a range of static pressure ratios and axial-velocity-density ratios (AVDR) at the design inlet condition. Flow velocity measurements showing the wave pattern in the cascade entrance region were obtained using a laser transit anemometer. From these measurements, some unique-incidence conditions were determined, thus relating the supersonic inlet Mach number to the inlet flow direction. The influence of static pressure ratio and AVDR on the blade passage flow and the blade-element performance is described, and an empirical correlation is used to show the influence of these two (independent) parameters on the exit flow angle and total-pressure loss for the design inlet condition
Partitioning Schemes and Non-Integer Box Sizes for the Box-Counting Algorithm in Multifractal Analysis
We compare different partitioning schemes for the box-counting algorithm in
the multifractal analysis by computing the singularity spectrum and the
distribution of the box probabilities. As model system we use the Anderson
model of localization in two and three dimensions. We show that a partitioning
scheme which includes unrestricted values of the box size and an average over
all box origins leads to smaller error bounds than the standard method using
only integer ratios of the linear system size and the box size which was found
by Rodriguez et al. (Eur. Phys. J. B 67, 77-82 (2009)) to yield the most
reliable results.Comment: 10 pages, 13 figure
The influence of self-citation corrections on Egghe's g index
The g index was introduced by Leo Egghe as an improvement of Hirsch's index h
for measuring the overall citation record of a set of articles. It better takes
into account the highly skewed frequency distribution of citations than the h
index. I propose to sharpen this g index by excluding the self-citations. I
have worked out nine practical cases in physics and compare the h and g values
with and without self-citations. As expected, the g index characterizes the
data set better than the h index. The influence of the self-citations appears
to be more significant for the g index than for the h index.Comment: 9 pages, 2 figures, submitted to Scientometric
Report drawn up on behalf of the Committee on Budgets on the fixing of the ECSC levies and on the ECSC operational budget for 1979 (Doc. 497/78). EP Working Documents, document 502/78, 11 December 1978
On the periodic variations of geomagnetic activity indices Ap and ap
International audienceYearly averages of geomagnetic activity indices Ap for the years 1967?1984 are compared to the respective averages of ?2·Bs, where v is the solar wind velocity and Bs is the southward interplanetary magnetic field (IMF) component. The correlation of both quantities is known to be rather good. Comparing the averages of Ap with ?2 and Bs separately we find that, during the declining phase of the solar cycle, ?2 and during the ascending phase Bs have more influence on Ap. According to this observation (using Fourier spectral analysis) the semiannual and 27 days, Ap variations for the years 1932?1993 were analysed separately for years before and after sunspot minima. Only those time-intervals before sunspot minima with a significant 27-day recurrent period of the IMF sector structure and those intervals after sunspot minima with a significant 28-28.5-day recurrent period of the sector structure were used. The averaged spectra of the two Ap data sets clearly show a period of 27 days before and a period of 28?29 days after sunspot minimum. Moreover, the phase of the average semiannual wave of Ap is significantly different for the two groups of data: the Ap variation maximizes near the equinoxes during the declining phase of the sunspot cycle and near the beginning of April and October during the ascending phase of the sunspot cycle, as predicted by the Russell-McPherron (R-M) mechanism. Analysing the daily variation of ap in an analogue manner, the same equinoctial and R-M mechanisms are seen, suggesting that during phases of the solar cycle, when ap depends more on the IMF-Bs component, the R-M mechanism is predominant, whereas during phases when ap increases as v increases the equinoctial mechanism is more likely to be effective
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