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Evaluation and comparison of satellite precipitation estimates with reference to a local area in the Mediterranean Sea
Precipitation is one of the major variables for many applications and disciplines related to water resources and the geophysical Earth system. Satellite retrieval systems, rain-gauge networks, and radar systems are complementary to each other in terms of their coverage and capability of monitoring precipitation. Satellite-rainfall estimate systems produce data with global coverage that can provide information in areas for which data from other sources are unavailable. Without referring to ground measurements, satellite-based estimates can be biased and, although some gauge-adjusted satellite-precipitation products have been already developed, an effective way of integrating multi-sources of precipitation information is still a challenge.In this study, a specific area, the Sicilia Island (Italy), has been selected for the evaluation of satellite-precipitation products based on rain-gauge data. This island is located in the Mediterranean Sea, with a particular climatology and morphology, which can be considered an interesting test site for satellite-precipitation products in the European mid-latitude area. Four satellite products (CMORPH, PERSIANN, PERSIANN-CCS, and TMPA-RT) and two GPCP-adjusted products (TMPA and PERSIANN Adjusted) have been selected. Evaluation and comparison of selected products is performed with reference to data provided by the rain-gauge network of the Island Sicilia and by using statistical and graphical tools. Particular attention is paid to bias issues shown both by only-satellite and adjusted products. In order to investigate the current and potential possibilities of improving estimates by means of adjustment procedures using GPCC ground precipitation, the data have been retrieved separately and compared directly with the reference rain-gauge network data set of the study area.Results show that bias is still considerable for all satellite products, then some considerations about larger area climatology, PMW-retrieval algorithms, and GPCC data are discussed to address this issue, along with the spatial and seasonal characterization of results. © 2013 Elsevier B.V
Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility
Issues of morphology, nucleation and growth of Ge cluster arrays deposited by
ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered.
Difference in nucleation of quantum dots during Ge deposition at low (<600 deg
C) and high (>600 deg. C) temperatures is studied by high resolution scanning
tunneling microscopy. The atomic models of growth of both species of Ge
huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at
low temperatures is explored. A problem of lowering of the array formation
temperature is discussed with the focus on CMOS compatibility of the entire
process; a special attention is paid upon approaches to reduction of treatment
temperature during the Si(001) surface pre-growth cleaning, which is at once a
key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array
formation process. The temperature of the Si clean surface preparation, the
final high-temperature step of which is, as a rule, carried out directly in the
MBE chamber just before the structure deposition, determines the compatibility
of formation process of Ge-QD-array based devices with the CMOS manufacturing
cycle. Silicon surface hydrogenation at the final stage of its wet chemical
etching during the preliminary cleaning is proposed as a possible way of
efficient reduction of the Si wafer pre-growth annealing temperature.Comment: 30 pages, 11 figure
Detecting Byzantine Attacks Without Clean Reference
We consider an amplify-and-forward relay network composed of a source, two
relays, and a destination. In this network, the two relays are untrusted in the
sense that they may perform Byzantine attacks by forwarding altered symbols to
the destination. Note that every symbol received by the destination may be
altered, and hence no clean reference observation is available to the
destination. For this network, we identify a large family of Byzantine attacks
that can be detected in the physical layer. We further investigate how the
channel conditions impact the detection against this family of attacks. In
particular, we prove that all Byzantine attacks in this family can be detected
with asymptotically small miss detection and false alarm probabilities by using
a sufficiently large number of channel observations \emph{if and only if} the
network satisfies a non-manipulability condition. No pre-shared secret or
secret transmission is needed for the detection of these attacks, demonstrating
the value of this physical-layer security technique for counteracting Byzantine
attacks.Comment: 16 pages, 7 figures, accepted to appear on IEEE Transactions on
Information Forensics and Security, July 201
Electron-doped phosphorene: A potential monolayer superconductor
We predict by first-principles calculations that the electron-doped
phosphorene is a potential BCS-like superconductor. The stretching modes at the
Brillouin-zone center are remarkably softened by the electron-doping, which
results in the strong electron-phonon coupling. The superconductivity can be
introduced by a doped electron density () above
cm, and may exist over the liquid helium temperature when cm. The maximum critical temperature is predicted to be
higher than 10 K. The superconductivity of phosphorene will significantly
broaden the applications of this novel material
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