5,582 research outputs found
Poisson to Random Matrix Transition in the QCD Dirac Spectrum
At zero temperature the lowest part of the spectrum of the QCD Dirac operator
is known to consist of delocalized modes that are described by random matrix
statistics. In the present paper we show that the nature of these eigenmodes
changes drastically when the system is driven through the finite temperature
cross-over. The lowest Dirac modes that are delocalized at low temperature
become localized on the scale of the inverse temperature. At the same time the
spectral statistics changes from random matrix to Poisson statistics. We
demonstrate this with lattice QCD simulations using 2+1 flavors of light
dynamical quarks with physical masses. Drawing an analogy with Anderson
transitions we also examine the mobility edge separating localized and
delocalized modes in the spectrum. We show that it scales in the continuum
limit and increases sharply with the temperature.Comment: 10 pages, 9 eps figures, a few references added and typos correcte
The Metallicity Dependence of the Fourier Components of RR Lyrae Light Curves is the Oosterhoff/Arp/Preston Period Ratio Effect in Disguise
The correlation of particular Fourier components of the light curves of RR
Lyrae variables with metallicity, discovered by Simon and later by Kovacs and
his coworkers, is shown to have the same explanation as the period ratios
(period shifts in log P) between RRab Lyrae variables that have the same
colors, amplitudes, and light-curve shapes but different metallicities. A
purpose of this paper is to demonstrate that the model which predicts the
period-metallicity relations is the mediating parameters of colors, amplitudes,
and light-curve shapes also explains the Simon/Kovacs et al. correlation
between period, Phi_31, and metallicity. The proof is made by demonstrating
that the combination of the first and third phase terms in a Fourier
decomposition of RRab light curves, called Phi_31 by Simon and Lee, varies
monotonically across the RR Lyrae instability strip in the same way that
amplitude, color, and rise time vary with period within the strip. The premise
of the model is that if horizontal branches at the RR Lyrae strip are stacked
in luminosity according to the metallicity, then there necessarily must be a
log period shift between RR Lyraes with different metallicities at the same
Phi_31 values. However, there are exceptions to the model. (...)Comment: 17 pages, 8 figures, 1 table. Accepted for publication in The A
Development of a novel color inhomogeneity test method for injection molded parts
Abstract
Nowadays most research and development concerning injection molded products are focused on their mechanical properties although visual appeal plays an even more important role on the market. There are several standards and recommendations for the testing of mechanical properties, but appearance cannot be quantified easily. The visual aspects are almost completely neglected, and there is not a commonly accepted method for measuring color inhomogeneity.
The appearance and color homogeneity of injection molded parts depends on the coloring method itself, the applied technology and several other conditions. The method used nowadays to evaluate color inhomogeneity is based on visual inspection by humans. This research focuses on developing a new and automated method that can replace visual inspection. The functionality and precision of the new method and software have been tested and compared with visual inspection to prove its applicability
A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
We have performed a detailed study of the pulsational and evolutionary
characteristics of 133 RR Lyrae stars in the globular cluster NGC5272 (M3)
using highly accurate BVI data taken on 5 separate epochs. M3 seems to contain
no less than ~32% of Blazhko stars, and the occurrence and characteristics of
the Blazhko effect have been analyzed in detail. We have identified a good
number (~ 14%) of overluminous RR Lyrae stars that are likely in a more
advanced evolutionary stage off the Zero Age Horizontal Branch (ZAHB). Physical
parameters (i.e. temperature, luminosity, mass) have been derived from (B--V)
colors and accurate color-temperature calibration, and compared with Horizontal
Branch evolutionary models and with the requirements of stellar pulsation
theory. Additional analysis by means of Fourier decomposition of the V light
curves confirms, as expected, that no metallicity spread is present in M3.
Evolution off the ZAHB does not affect [Fe/H] determinations, whereas Blazhko
stars at low amplitude phase do affect [Fe/H] distributions as they appear more
metal-rich. Absolute magnitudes derived from Fourier coefficients might provide
useful average estimates for groups of stars, if applicable, but do not give
reliable {\em individual} values. Intrinsic colors derived from Fourier
coefficients show significant discrepancies with the observed ones, hence the
resulting temperatures and temperature-related parameters are unreliable.Comment: 86 pages, 19 figures, 13 tables, in press A
The MACHO Project LMC Variable Star Inventory. IX. Frequency Analysis of the First Overtone RR Lyrae Stars and the Indication for Nonradial Pulsations
More than 1300 variables classified provisionally as first overtone RR Lyrae
pulsators in the MACHO variable star database of the Large Magellanic Cloud
(LMC) have been subjected to standard frequency analysis. Based on the remnant
power in the prewhitened spectra, we found 70% of the total population to be
monoperiodic. The remaining 30% (411 stars) are classified as one of 9 types
according to their frequency spectra. Several types of RR Lyrae pulsational
behavior are clearly identified here for the first time. Together with the
earlier discovered double-mode (fundamental & first overtone) variables this
study increased the number of the known double-mode stars in the LMC to 181.
During the total 6.5yr time span of the data, 10% of the stars show strong
period changes. We also discovered two additional types of multifrequency
pulsators with low occurrence rates of 2% for each. In the first type there
remains one closely spaced component after prewhitening by the main pulsation
frequency. In the second type the number of remnant components is two, they are
also closely spaced, and, in addition, they are symmetric in their frequency
spacing relative to the central component. This latter type of variables is
associated with their relatives among the fundamental pulsators, known as
Blazhko variables. Their high frequency (~20%) among the fundamental mode
variables versus the low occurrence rate of their first overtone counterparts
makes it more difficult to explain Blazhko phenomenon by any theory depending
mainly on the role of aspect angle or magnetic field. Current theoretical
models invoke nonradial pulsation components in these stars.Comment: 20 pages, 21 figures (bitmapped), 7 tables, to appear in Ap.
Non equilibrium inertial dynamics of colloidal systems
We consider the properties of a one dimensional fluid of brownian inertial
hard-core particles, whose microscopic dynamics is partially damped by a
heat-bath. Direct interactions among the particles are represented as binary,
instantaneous elastic collisions. Collisions with the heath bath are accounted
for by a Fokker-Planck collision operator, whereas direct collisions among the
particles are treated by a well known method of kinetic theory, the Revised
Enskog Theory. By means of a time multiple time-scale method we derive the
evolution equation for the average density. Remarkably, for large values of the
friction parameter and/or of the mass of the particles we obtain the same
equation as the one derived within the dynamic density functional theory (DDF).
In addition, at moderate values of the friction constant, the present method
allows to study the inertial effects not accounted for by DDF method. Finally,
a numerical test of these corrections is provided.Comment: 13 pages+ 3 Postscript figure
Towards a Deadline-Based Simulation Experimentation Framework Using Micro-Services Auto-Scaling Approach
There is growing number of research efforts in developing auto-scaling algorithms and tools for cloud resources. Traditional performance metrics such as CPU, memory and bandwidth usage for scaling up or down resources are not sufficient for all applications. For example, modeling and simulation experimentation is usually expected to yield results within a specific timeframe. In order to achieve this, often the quality of experiments is compromised either by restricting the parameter space to be explored or by limiting the number of replications required to give statistical confidence. In this paper, we present early stages of a deadline-based simulation experimentation framework using a micro-services auto-scaling approach. A case study of an agent-based simulation of a population physical activity behavior is used to demonstrate our framework
SZTAKI desktop grid: a modular and scalable way of building large computing grids
So far BOINC based desktop grid systems have been applied at the global computing level. This paper describes an extended version of BOINC called SZTAKI desktop grid (SZDG) that aims at using desktop grids (DGs) at local (enterprise/institution) level. The novelty of SZDG is that it enables the hierarchical organisation of local DGs, i.e., clients of a DG can be DGs at a lower level that can take work units from their higher level DG server. More than that, even clusters can be connected at the client level and hence work units can contain complete MPI programs to be run on the client clusters. In order to easily create master/worker type DG applications a new API, called as the DC-API has been developed. SZDG and DC-API has been successfully applied both at the global and local level, both in academic institutions and in companies to solve problems requiring large computing power
From Design to Production Control Through the Integration of Engineering Data Management and Workflow Management Systems
At a time when many companies are under pressure to reduce "times-to-market"
the management of product information from the early stages of design through
assembly to manufacture and production has become increasingly important.
Similarly in the construction of high energy physics devices the collection of
(often evolving) engineering data is central to the subsequent physics
analysis. Traditionally in industry design engineers have employed Engineering
Data Management Systems (also called Product Data Management Systems) to
coordinate and control access to documented versions of product designs.
However, these systems provide control only at the collaborative design level
and are seldom used beyond design. Workflow management systems, on the other
hand, are employed in industry to coordinate and support the more complex and
repeatable work processes of the production environment. Commercial workflow
products cannot support the highly dynamic activities found both in the design
stages of product development and in rapidly evolving workflow definitions. The
integration of Product Data Management with Workflow Management can provide
support for product development from initial CAD/CAM collaborative design
through to the support and optimisation of production workflow activities. This
paper investigates this integration and proposes a philosophy for the support
of product data throughout the full development and production lifecycle and
demonstrates its usefulness in the construction of CMS detectors.Comment: 18 pages, 13 figure
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