74 research outputs found
A Risk-Based Methodology and Tool Combining Threat Analysis and Power System Security Assessment
A thorough investigation of power system security requires the analysis of the vulnerabilities to natural and man-related threats which potentially trigger multiple contingencies. In particular, extreme weather events are becoming more and more frequent due to climate changes and often cause large load disruptions on the system, thus the support for security enhancement gets tricky. Exploiting data coming from forecasting systems in a security assessment environment can help assess the risk of operating power systems subject to the disturbances provoked by the weather event itself. In this context, the paper proposes a security assessment methodology, based on an updated definition of risk suitable for power system risk evaluations. Big data analytics can be useful to get an accurate model for weather-related threats. The relevant software (SW) platform integrates the security assessment methodology with prediction systems which provide short term forecasts of the threats affecting the system. The application results on a real wet snow threat scenario in the Italian High Voltage grid demonstrate the effectiveness of the proposed approach with respect to conventional security approaches, by complementing the conventional "N - 1" security criterion and exploiting big data to link the security assessment phase to the analysis of incumbent threat
First Estimations of Cosmological Parameters From BOOMERANG
The anisotropy of the cosmic microwave background radiation contains
information about the contents and history of the universe. We report new
limits on cosmological parameters derived from the angular power spectrum
measured in the first Antarctic flight of the BOOMERANG experiment. Within the
framework of inflation-motivated adiabatic cold dark matter models, and using
only weakly restrictive prior probabilites on the age of the universe and the
Hubble expansion parameter , we find that the curvature is consistent with
flat and that the primordial fluctuation spectrum is consistent with scale
invariant, in agreement with the basic inflation paradigm. We find that the
data prefer a baryon density above, though similar to, the
estimates from light element abundances and big bang nucleosynthesis. When
combined with large scale structure observations, the BOOMERANG data provide
clear detections of both dark matter and dark energy contributions to the total
energy density , independent of data from high redshift
supernovae.Comment: As submitted to PRD, revised longer version with an additional figur
Images of the Early Universe from the BOOMERanG experiment
The CMB is the fundamental tool to study the properties of the early universe and of the
universe at large scales. In the framework of the Hot Big Bang model, when we look to
the CMB we look back in time to the end of the plasma era, at a redshift ~ 1000, when
the universe was ~ 50000 times younger, ~ 1000 times hotter and ~ 10^9 times denser
than today. The image of the CMB can be used to study the physical processes there, to
infer what happened before, and also to study the background geometry of our Universe
CMB Analysis of Boomerang & Maxima & the Cosmic Parameters {Omega_tot,Omega_b h^2,Omega_cdm h^2,Omega_Lambda,n_s}
We show how estimates of parameters characterizing inflation-based theories
of structure formation localized over the past year when large scale structure
(LSS) information from galaxy and cluster surveys was combined with the rapidly
developing cosmic microwave background (CMB) data, especially from the recent
Boomerang and Maxima balloon experiments. All current CMB data plus a
relatively weak prior probability on the Hubble constant, age and LSS points to
little mean curvature (Omega_{tot} = 1.08\pm 0.06) and nearly scale invariant
initial fluctuations (n_s =1.03\pm 0.08), both predictions of (non-baroque)
inflation theory. We emphasize the role that degeneracy among parameters in the
L_{pk} = 212\pm 7 position of the (first acoustic) peak plays in defining the
range upon marginalization over other variables. Though the CDM
density is in the expected range (\Omega_{cdm}h^2=0.17\pm 0.02), the baryon
density Omega_bh^2=0.030\pm 0.005 is somewhat above the independent 0.019\pm
0.002 nucleosynthesis estimate. CMB+LSS gives independent evidence for dark
energy (Omega_\Lambda=0.66\pm 0.06) at the same level as from supernova (SN1)
observations, with a phenomenological quintessence equation of state limited by
SN1+CMB+LSS to w_Q<-0.7 cf. the w_Q=-1 cosmological constant case.Comment: 11 pages, 3 figs., in Proc. IAU Symposium 201 (PASP), CITA-2000-6
The Quintessential CMB, Past & Future
The past, present and future of cosmic microwave background (CMB) anisotropy
research is discussed, with emphasis on the Boomerang and Maxima balloon
experiments. These data are combined with large scale structure (LSS)
information and high redshift supernova (SN1) observations to explore the
inflation-based cosmic structure formation paradigm. Here we primarily focus on
a simplified inflation parameter set, {omega_b,omega_{cdm},Omega_{tot},
Omega_Q,w_Q, n_s,tau_C, sigma_8}. After marginalizing over the other cosmic and
experimental variables, we find the current CMB+LSS+SN1 data gives
Omega_{tot}=1.04\pm 0.05, consistent with (non-baroque) inflation theory.
Restricting to Omega_{tot}=1, we find a nearly scale invariant spectrum, n_s
=1.03 \pm 0.07. The CDM density, omega_{cdm}=0.17\pm 0.02, is in the expected
range, but the baryon density, omega_b=0.030\pm 0.004, is slightly larger than
the current nucleosynthesis estimate. Substantial dark energy is inferred,
Omega_Q\approx 0.68\pm 0.05, and CMB+LSS Omega_Q values are compatible with the
independent SN1 estimates. The dark energy equation of state, parameterized by
a quintessence-field pressure-to-density ratio w_Q, is not well determined by
CMB+LSS (w_Q<-0.3 at 95%CL), but when combined with SN1 the resulting w_Q<-0.7
limit is quite consistent with the w_Q=-1 cosmological constant case. Though
forecasts of statistical errors on parameters for current and future
experiments are rosy, rooting out systematic errors will define the true
progress.Comment: 14 pages, 3 figs., in Proc. CAPP-2000 (AIP), CITA-2000-6
Noise estimation in CMB time-streams and fast map-making. Application to the BOOMERanG98 data
We describe here an iterative method for jointly estimating the noise power
spectrum from a CMB experiment's time-ordered data, together with the
maximum-likelihood map. We test the robustness of this method on simulated
Boomerang datasets with realistic noise.Comment: 7 pages, 6 figures, to appear in proc. of the MPA/ESO/MPA conference
"Mining the Sky", Garching, July 31 - August 4 200
First results from the BOOMERanG experiment
We report the first results from the BOOMERanG experiment, which mapped at
90, 150, 240 and 410 GHz a wide (3%) region of the microwave sky with minimal
local contamination. From the data of the best 150 GHz detector we find
evidence for a well defined peak in the power spectrum of temperature
fluctuations of the Cosmic Microwave Background, localized at , with an amplitude of . The location, width and
amplitude of the peak is suggestive of acoustic oscillations in the primeval
plasma. In the framework of inflationary adiabatic cosmological models the
measured spectrum allows a Bayesian estimate of the curvature of the Universe
and of other cosmological parameters. With reasonable priors we find and (68%C.L.) in excellent agreement
with the expectations from the simplest inflationary theories. We also discuss
the limits on the density of baryons, of cold dark matter and on the
cosmological constant.Comment: Proc. of the CAPP2000 conference, Verbier, 17-28 July 200
Detection of anisotropy in the Cosmic Microwave Background at horizon and sub-horizon scales with the BOOMERanG experiment
BOOMERanG has recently resolved structures on the last scattering surface at
redshift 1100 with high signal to noise ratio. We review the technical
advances which made this possible, and we focus on the current results for maps
and power spectra, with special attention to the determination of the total
mass-energy density in the Universe and of other cosmological parameters
The Cosmic Background Radiation circa nu2K
We describe the implications of cosmic microwave background (CMB)
observations and galaxy and cluster surveys of large scale structure (LSS) for
theories of cosmic structure formation, especially emphasizing the recent
Boomerang and Maxima CMB balloon experiments. The inflation-based cosmic
structure formation paradigm we have been operating with for two decades has
never been in better shape. Here we primarily focus on a simplified inflation
parameter set, {omega_b,omega_{cdm},Omega_{tot}, Omega_\Lambda,n_s,\tau_C,
\sigma_8}. Combining all of the current CMB+LSS data points to the remarkable
conclusion that the local Hubble patch we can access has little mean curvature
(Omega_{tot}=1.08\pm 0.06) and the initial fluctuations were nearly scale
invariant (n_s=1.03\pm 0.08), both predictions of (non-baroque) inflation
theory. The baryon density is found to be slightly larger than that preferred
by independent Big Bang Nucleosynthesis estimates (omega_b=0.030\pm 0.005 cf.
0.019\pm 0.002). The CDM density is in the expected range (omega_{cdm}=0.17 \pm
0.02). Even stranger is the CMB+LSS evidence that the density of the universe
is dominated by unclustered energy akin to the cosmological constant
(Omega_\Lambda=0.66\pm 0.06), at the same level as that inferred from high
redshift supernova observations. We also sketch the CMB+LSS implications for
massive neutrinos.Comment: 7 pages, 4 figs., in Proc. Neutrino 2000 (Elsevier), CITA-2000-6
Cosmology from Maxima-1, Boomerang and COBE/DMR CMB Observations
Recent results from BOOMERANG-98 and MAXIMA-1, taken together with COBE-DMR,
provide consistent and high signal-to-noise measurements of the CMB power
spectrum at spherical harmonic multipole bands over 2<\ell\lta800. Analysis
of the combined data yields 68% (95%) confidence limits on the total density,
, the baryon
density, , and
the scalar spectral tilt, .
These data are consistent with inflationary initial conditions for structure
formation. Taken together with other cosmological observations, they imply the
existence of both non-baryonic dark matter and dark energy in the universe.Comment: 5 Pages, 2 Figures, Changes to match published versio
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