48 research outputs found
The Role of the Direct Normal Irradiance (DNI) Forecasting in the Operation of Solar Concentrating Plants
Abstract A method capable of forecasting the DHI (Diffuse Horizontal Irradiance), DNI (Direct Normal Irradiance) and GHI (Global Horizontal Irradiance) for targeted locations involved in the installation of concentrating solar plants has been developed at the Casaccia Center of the ENEA located near Rome (Italy). These forecasts are issued daily at 00:00 in the morning and cover a temporal arc of four days which includes the actual day as well as the following three days in hourly time resolution. The method develops and expands upon information taken from Internet and these forecasts are presented as an example on the Internet site for five localities of ENEA interest: http://www.solaritaly.enea.it/Previsioni/PrevisioniEn.php; they are potentially available for every location. The RMSE% of the DNI forecasts on daily basis compared with the measures is 10%. In the Internet age, old methods must be updated to take into account the immense potential available today on the net
Solar Radiation Maps
[EN]Solar maps are very interesting tools to describe the characteristics of a region from the solar radiation point of view, and can be applied in atmospheric sciences and for energy engineering. To make them possible, a solar radiation numerical model is proposed. This one allows us to estimate radiation values on any point on earth. The model takes into account the terrain surface conditions and the cast shadows. The procedure uses 2-D adaptive triangles meshes built refining according to surface and albedo characteristics. Solar irradiance values are obtained for clear sky conditions. Using clear sky index as a conversion factor, real sky values are computed in terms of irradiance or irradiation with a desired time step. Finally, the solar radiation maps are obtained for all the domain
Boosting OMD for Almost Free Authentication of Associated Data
We propose pure OMD (p-OMD) as a new variant of the Offset Merkle-DamgÄrd (OMD) authenticated encryption scheme. Our new scheme inherits all desirable security features of OMD while having a more compact structure and providing higher efficiency. The original OMD scheme, as submitted to the CAESAR competition, couples a single pass of a variant of the Merkle-DamgÄrd (MD) iteration with the counter-based XOR MAC algorithm to provide privacy and authenticity. Our improved p-OMD scheme dispenses with the XOR MAC algorithm and is purely based on the MD iteration; hence, the name ``pure'' OMD. To process a message of blocks and associated data of blocks, OMD needs calls to the compression function while p-OMD only requires max{}+ calls. Therefore, for a typical case where , p-OMD makes just calls to the compression function; that is, associated data is processed almost freely compared to OMD. We prove the security of p-OMD under the same standard assumption (pseudo-randomness of the compression function) as made in OMD; moreover, the security bound for p-OMD is the same as that of OMD, showing that the modifications made to boost the performance are without any loss of security
Time-scaled evolutionary analysis of the transmission and antibiotic resistance dynamics of Staphylococcus aureus CC398
Staphylococcus aureus clonal complex 398 (CC398) is associated with disease in humans and livestock, and its origins and transmission have generated considerable interest. We performed a time-scaled phylogenetic analysis of CC398, including sequenced isolates from the United Kingdom (Scotland), along with publicly available genomes. Using state-of-the-art methods for mapping traits onto phylogenies, we quantified transitions between host species to identify sink and source populations for CC398 and employed a novel approach to investigate the gain and loss of antibiotic resistance in CC398 over time. We identified distinct human- and livestock-associated CC398 clades and observed multiple transmissions of CC398 from livestock to humans and between countries, lending quantitative support to previous reports. Of note, we identified a subclade within the livestock-associated clade comprised of isolates from hospital environments and newborn babies, suggesting that livestock-associated CC398 is capable of onward transmission in hospitals. In addition, our analysis revealed significant differences in the dynamics of resistance to methicillin and tetracycline related to contrasting historical patterns of antibiotic usage between the livestock industry and human medicine. We also identified significant differences in patterns of gain and loss of different tetracycline resistance determinants, which we ascribe to epistatic interactions between the resistance genes and/or differences in the modes of inheritance of the resistance determinants
Breaking Symmetric Cryptosystems Using Quantum Period Finding
Due to Shor's algorithm, quantum computers are a severe threat for public key
cryptography. This motivated the cryptographic community to search for
quantum-safe solutions. On the other hand, the impact of quantum computing on
secret key cryptography is much less understood. In this paper, we consider
attacks where an adversary can query an oracle implementing a cryptographic
primitive in a quantum superposition of different states. This model gives a
lot of power to the adversary, but recent results show that it is nonetheless
possible to build secure cryptosystems in it.
We study applications of a quantum procedure called Simon's algorithm (the
simplest quantum period finding algorithm) in order to attack symmetric
cryptosystems in this model. Following previous works in this direction, we
show that several classical attacks based on finding collisions can be
dramatically sped up using Simon's algorithm: finding a collision requires
queries in the classical setting, but when collisions happen
with some hidden periodicity, they can be found with only queries in the
quantum model.
We obtain attacks with very strong implications. First, we show that the most
widely used modes of operation for authentication and authenticated encryption
e.g. CBC-MAC, PMAC, GMAC, GCM, and OCB) are completely broken in this security
model. Our attacks are also applicable to many CAESAR candidates: CLOC, AEZ,
COPA, OTR, POET, OMD, and Minalpher. This is quite surprising compared to the
situation with encryption modes: Anand et al. show that standard modes are
secure with a quantum-secure PRF.
Second, we show that Simon's algorithm can also be applied to slide attacks,
leading to an exponential speed-up of a classical symmetric cryptanalysis
technique in the quantum model.Comment: 31 pages, 14 figure
Comportamento del metabolismo basale dopo introduzione di sulfamidici
In questo lavoro l?a. studia il comportamento del M. B. di fronte alla somministrazione di sulfamidici in soggetti sani e in alcuni soggetti affetti da M. di Basedow.
L'A. ha osservato che dopo somministrazione prolungata ( cinque giorni) di sulfamidici (paraaminobenzesulfonamide) si ha, sia in soggetti senza particolare turbe del ricambio, sia in soggetti in cui il ricambio energetico Ăš esaltato per condizioni patologiche (M. di Basedow) un piĂč o meno costante abbassamento del M. B.
L'A. ritiene probabile, per ora almeno, che l'abbassamento di detta costante debba riportarsi ad una diminuzione di OÂČ dei tessuti ed organi dovuta verosimilmente ad una azione inibitrice del sulfamidico sul sistema enzimatico ossidoriduttivo che presiede alla respirazione interna dei tessuti
Thermal, pressure and wind fields at ground level in the area of the Italian base at Terra Nova Bay, Victoria Land, Antarctica, as observed by a network of automatic weather stations
Ground temperature, pressure and wind speed
monthly averages in the area of the Italian Station at Terra Nova Bay,
Antarctica, were analyzed for the period 1987â1991 by means of a network of nine
AWS (automatic weather stations). Spatial configurations of temperature show a
well-defined, relatively warm island in the area of Terra Nova Bay, between
Drygalsky and Campbell ice tongues, throughout the year. A second warm island is
present to the north along the coast, between Aviator and Mariner ice tongues,
for most of the year. From February to March a rapid drop in temperature is
observed at all stations. A strong thermal gradient develops during February,
March, April and October, November, December, between the coastal region and
inner highlands. The baric configuration follows the elevation of the area.
Annual average pressure and temperature as functions of stations altitude show
linear trends. Severe katabatic wind episodes are recorded at all stations, with
wind speed exceeding 25 m sâ1 and direction following the orographic
features of the inner areas. Co-occurrences of these episodes were observed for
stations located along stream lines of cold air drainage. The autocorrelation
function of maximum wind speed time series shows wind persistence of 2â3 days
and wind periodicity of about one week