35 research outputs found
A framework for usage management
This thesis proposes a formal framework for usage management in distributed systems. The principles of system design are applied in order to standardize certain features of the framework, such as the operational semantics, and leave free of standards areas that necessitate choice and innovation. The framework enables use of multiple policy languages, and dynamic interpretation of usage policies in different computing environments. In addition, the framework provides formal semantics to reason about interoperability of policies with respect to computing environments. The use of this framework in different usage management scenarios is demonstrated including multi-level security, cloud computing and digital rights management (DRM) systems. Furthermore, DRM is cast in a setting that allows the modeling of a number of current approaches within a game theoretic setting. Current strategies that attempt to influence the outcome of such games are analyzed, and a new type of architectural infrastructure that makes novel use of a trust authority is considered in order to create a suitable environment for constructing DRM games that may prove useful in the future
On the Normalization of the QSO's Lyman alpha Forest Power Spectrum
The calculation of the transmission power spectrum of QSO's Lyman alpha
absorption requires two parameters for the normalization: the continuum Fc and
mean transmission, i.e. average of e^{-tau}. Traditionally, the continuum is
obtained by a polynomial fitting truncating it at a lower order, and the mean
transmission is calculated over the entire wavelength range considered. The
flux F is then normalized by the average of Fc e^{-tau}. However, the
fluctuations in the transmitted flux are significantly correlated with the
local background flux on scales for which the field is intermittent. In this
paper, we develop a self-normalization algorithm of the transmission power
spectrum based on a multiresolution analysis. This self-normalized power
spectrum estimator needs neither a continuum fitting, nor pre-determining the
mean transmission. With simulated samples, we show that the self-normalization
algorithm can perfectly recover the transmission power spectrum from the flux
regardless of how the continuum varies with wavelength. We also show that the
self-normalized power spectrum is also properly normalized by the mean
transmission. Moreover, this power spectrum estimator is sensitive to the
non-linear behavior of the field. That is, the self-normalized power spectrum
estimator can distinguish between fields with or without the
fluctuation-background correlation. This cannot be accomplished by the power
spectrum with the normalization by an overall mean transmission. Therefore, the
self-normalized power spectrum would be useful for the discrimination among
models without the uncertainties caused by free (or fitting) parameters.Comment: 24 pages, 8 figures, to appear in ApJ tentatively in the Nov 1 2001
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Intermittent behavior of cosmic mass field revealed by QSO's Ly_alpha forests
The intermittent behavior of the space-scale distribution of Ly
transmitted flux of QSO HS1700+64 has been analyzed via a discrete wavelet
transform. We found that there are strong indications of intermittency on
scales down to about 10 kpc. These are: 1.) the probability
distribution function of the local fluctuations of the flux is significantly
long-tailed on small scales, and 2.) the local power spectrum of the flux shows
prominent spiky structures on small scales. Moreover, the local power spectrum
averaged on regions with different sizes shows similar spiky structures.
Therefore, the random mass density field traced by the Ly forests is
rougher on smaller scales, consistent with singular clustering.Comment: Accepted for publication in ApJ Letters, 12 pages, 3 figure
Power spectrum and intermittency of the transmitted flux of QSOs Ly-alpha absorption spectra
Using a set of 28 high resolution, high signal to noise ratio (S/N) QSO
Ly-alpha absorption spectra, we investigate the non-Gaussian features of the
transmitted flux fluctuations, and their effect upon the power spectrum of this
field. We find that the spatial distribution of the local power of the
transmitted flux on scales k >= 0.05 s/km is highly spiky or intermittent. The
probability distribution functions (PDFs) of the local power are long-tailed.
The power on small scales is dominated by small probability events, and
consequently, the uncertainty in the power spectrum of the transmitted flux
field is generally large. This uncertainty arises due to the slow convergence
of an intermittent field to a Gaussian limit required by the central limit
theorem (CLT). To reduce this uncertainty, it is common to estimate the error
of the power spectrum by selecting subsamples with an "optimal" size. We show
that this conventional method actually does not calculate the variance of the
original intermittent field but of a Gaussian field. Based on the analysis of
intermittency, we propose an algorithm to calculate the error. It is based on a
bootstrap re-sampling among all independent local power modes. This estimation
doesn't require any extra parameter like the size of the subsamples, and is
sensitive to the intermittency of the fields. This method effectively reduces
the uncertainty in the power spectrum when the number of independent modes
matches the condition of the CLT convergence.Comment: 26 pages (incl. figures). Accepted for publication in MNRA
A Unified Fitting of HI and HeII Ly\alpha Transmitted Flux of QSO HE2347 with LCDM Hydrodynamic Simulations
Using cosmological hydrodynamic simulations of the LCDM model, we present a
comparison between the simulation sample and real data sample of HI and HeII
Ly\alpha transmitted flux in the absorption spectra of the QSO HE2347-4342. The
LCDM model is successful in simultaneously explaining the statistical features
of both HI and HeII Ly\alpha transmitted flux. It includes: 1.) the power
spectra of the transmitted flux of HI and HeII can be well fitted on all scales
> 0.28h^{-1} Mpc for H, and > 1.1h^{-1} Mpc for He; 2.) the Doppler parameters
of absorption features of HeII and HI are found to be turbulent-broadening; 3.)
the ratio of HeII to HI optical depths are substantially scattered, due to the
significant effect of noise. A large part of the \eta-scatter is due to the
noise in the HeII flux. However, the real data contain more low-\eta events
than simulation sample. This discrepancy may indicate that the mechanism
leading extra fluctuations upon the simulation data, such as a fluctuating UV
radiation background, is needed. Yet, models of these extra fluctuations should
satisfy the constraints: 1.) if the fluctuations are Gaussian, they should be
limited by the power spectra of observed HI and HeII flux; 2.) if the
fluctuations are non-Gaussian, they should be limited by the observed
non-Gaussian features of the HI and HeII flux.Comment: 21 pages, 7 figs, ApJ in pres
Log-Poisson Hierarchical Clustering of Cosmic Neutral Hydrogen and Ly-alpha Transmitted Flux of QSO Absorption Spectrum
we study, in this paper, the non-Gaussian features of the mass density field
of neutral hydrogen fluid and the Ly-alpha transmitted flux of QSO absorption
spectrum from the point-of-view of self-similar log-Poisson hierarchy. It has
been shown recently that, in the scale range from the onset of nonlinear
evolution to dissipation, the velocity and mass density fields of cosmic baryon
fluid are extremely well described by the She-Leveque's scaling formula, which
is due to the log-Poisson hierarchical cascade. Since the mass density ratio
between ionized hydrogen to total hydrogen is not uniform in space, the mass
density field of neutral hydrogen component is not given by a similar mapping
of total baryon fluid. Nevertheless, we show, with hydrodynamic simulation
samples of the concordance CDM universe, that the mass density field
of neutral hydrogen, is also well described by the log-Poisson hierarchy. We
then investigate the field of Ly transmitted flux of QSO absorption
spectrum. Due to redshift distortion, Ly transmitted flux fluctuations
are no longer to show all features of the log-Poisson hierarchy. However, some
non-Gaussian features predicted by the log-Poisson hierarchy are not affected
by the redshift distortion. We test these predictions with the high resolution
and high S/N data of quasars Ly absorption spectra. All results given
by real data, including -hierarchy, high order moments and scale-scale
correlation, are found to be well consistent with the log-Poisson hierarchy. We
compare the log-Poisson hierarchy with the popular log-normal model of the
Ly transmitted flux. The later is found to yield too strong
non-Gaussianity at high orders, while the log-Poisson hierarchy is in agreement
with observed data.Comment: 24 pages, 9 figures, accepted by Ap
Managed Control of Composite Cloud Systems
Cloud providers have just begun to provide primitive functionality enabling users to configure and easily provision resources, primarily in the infrastructure as a service domain. In order to effectively manage cloud resources in an automated fashion, systems must automate quality-of-service (QoS) metric measurement as a part of a larger usage management strategy. Collected metrics can then be used within control loops to manage and provision cloud resources. This basic approach can be scaled to monitor the use of system artifacts as well as simple QoS parameters, and can also address the needs of large systems spanning the boundaries of single service providers though the problem seems to moving toward intractability
Non-Gaussian Features of Transmitted Flux of QSO's Ly Absorption: Intermittent Exponent
We calculate the structure function and intermittent exponent of the 1.) Keck
data, which consists of 29 high resolution, high signal to noise ratio (S/N)
QSO Ly absorption spectra, and 2.)the Ly forest simulation
samples produced via the pseudo hydro scheme for the low density cold dark
matter (LCDM) model and warm dark matter (WDM) model with particle mass
and 1000 eV. These two measures detect not only
non-gaussianities, but also the type of non-gaussianty in the the field. We
find that, 1.) the structure functions of the simulation samples are
significantly larger than that of Keck data on scales less than about 100
h kpc, 2.) the intermittent exponent of the simulation samples is more
negative than that of Keck data on all redshifts considered, 3.) the
order-dependence of the structure functions of simulation samples are closer to
the intermittency of hierarchical clustering on all scales, while the Keck data
are closer to a lognormal field on small scales. These differences are
independent of noise and show that the intermittent evolution modeled by the
pseudo-hydro simulation is substantially different from observations, even
though they are in good agreement in terms of second and lower order
statistics. (Abridged)Comment: 17 pages, 13 figures. Accepted by Ap