138,774 research outputs found
Co-location detection on the Cloud
In this work we focus on the problem of co-location as a
first step of conducting Cross-VM attacks such as Prime and Probe or
Flush+Reload in commercial clouds. We demonstrate and compare three
co-location detection methods namely, cooperative Last-Level Cache (LLC)
covert channel, software profiling on the LLC and memory bus locking.
We conduct our experiments on three commercial clouds, Amazon EC2,
Google Compute Engine and Microsoft Azure. Finally, we show that
both cooperative and non-cooperative co-location to specific targets on
cloud is still possible on major cloud services
La Freccia Rossa: An IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate
The dynamics of the high-velocity compact molecular cloud CO-0.40-0.22 have
been interpreted as evidence for a black hole within 60
pc of Sgr A*. Recently, Oka et al. have identified a compact
millimetre-continuum source, CO-0.40-0.22*, with this candidate black hole.
Here we present a collation of radio and infrared data at this location. ATCA
constraints on the radio spectrum, and the detection of a mid-infrared
counterpart, are in tension with an Sgr A*-like model for CO-0.40-0.22* despite
the comparable bolometric to Eddington luminosity ratios under the IMBH
interpretation. A protostellar-disk scenario is, however, tenable.
CO-0.40-0.22(*) is associated with an arrowhead-shaped infrared-dark cloud
(which we call the Freccia Rossa). Radio-continuum observations reveal a
candidate HII region associated with the system. If the
km s systemic velocity of CO-0.40-0.22 is common to the entire Freccia
Rossa system, we hypothesise that it is the remnant of a high-velocity cloud
that has plunged into the Milky Way from the Galactic halo.Comment: 6 pages, 3 figures, submitted to MNRAS Letter
A self-sufficient approach for GERB cloudy radiance detection.
Geostationary Earth Radiation Budget (GERB) is the broadband radiometer onboard the Meteosat Second Generation (MSG) platform, launched at the end of August 2002 and still in commissioning phase. GERB data is planned to be used in many applications concerning Earth Radiation Budget (ERB) calculation. In order to evaluate the impact of clouds on ERB, a cloud detection is required and, at present, a cloud mask based on higher spatial and spectral resolution data acquired by Spinning Enhanced Visible and Infrared Imager (SEVIRI), the imager onboard the same MSG platform, is planned to be used in order to identify cloudy GERB soundings.
As an alternative, a self-sufficient (only based on GERB data) method (OCA, the One-channel Cloudy-radiance-detection Approach) is proposed, as a time-saving and, probably, more suitable solution than the planned co-location approach.
In this paper, preliminary results obtained by using several years of Meteosat data as well as GERB synthetic radiances (produced from Meteosat-7 observations) are presented. It is shown how results obtained by using GERB data alone can be comparable (and better in terms of number and spatial distribution of clear-sky GERB soundings identified) to the ones achieved if the co-location of a higher resolution cloud mask is use
Detection of Carbon Monoxide within the Magellanic Bridge
The Mopra 22m and SEST 15m telescopes have been used to detect and partially
map a region of 12CO(1-0) line emission within the Magellanic Bridge, a region
lying between the Large and Small Magellanic Clouds. The emission appears to be
embedded in a cloud of neutral hydrogen, and is in the vicinity of an IRAS
source. The CO emission region is found to have a 60um/100um flux density ratio
typical for 12CO(1-0) detections within the SMC, although it has a
significantly lower 12CO brightness and velocity width. These suggest that the
observed region is of a low metallicity, supporting earlier findings that the
Magellanic Bridge is not as evolved as the SMC and Magellanic Stream, which are
themselves of a lower metallicity than the Galaxy. Our observations, along with
empirical models based on SMC observations, indicate that the radius of the
detected CO region has an upper limit of ~16 pc. This detection is, to our
knowledge, the first detection of CO emission from the Magellanic Bridge and is
the only direct evidence of star formation through molecular cloud collapse in
this region.Comment: 8 pages, 6 Figures. LaTeX. Accepted for publication by MNRA
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Automatic Detection of Clear-Sky Periods From Irradiance Data
Recent degradation studies have highlighted the importance of considering cloud cover when calculating degradation rates, finding more reliable values when the data are restricted to clear sky periods. Several automated methods of determining clear sky periods have been previously developed, but parameterizing and testing the models has been difficult. In this paper, we use clear sky classifications determined from satellite data to develop an algorithm that determines clear sky periods using only measured irradiance values and modeled clear sky irradiance as inputs. This method is tested on global horizontal irradiance (GHI) data from ground collectors at six sites across the United States and compared against independent satellite-based classifications. First, 30 separate models were optimized on each individual site at GHI data intervals of 1, 5, 10, 15, and 30 min (sampled on the first minute of the interval). The models had an average F0.5 score of 0.949 ± 0.035 on a holdout test set. Next, optimizations were performed by aggregating data from different locations at the same interval, yielding one model per data interval. This paper yielded an average F0.5 of 0.946 ± 0.037. A final, 'universal' optimization that was trained on data from all sites at all intervals provided an F0.5 score of 0.943 ± 0.040. The optimizations all provide improvements on a prior, unoptimized clear sky detection algorithm that produces F0.5 scores that average to 0.903 ± 0.067. Our paper indicates that a single algorithm can accurately classify clear sky periods across locations and data sampling intervals
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