FOS: a low-power cache organization for multicores

The Journal of Supercomputing - The cache hierarchy of current multicore processors typically consists of one or two levels of private caches per core and a large shared last-level cache. This...     

Use of high-resolution satellite imagery in an integrated model to predict the distribution of shade coffee tree hybrid zones

In New Caledonia (21°S, 165°E), shade-grown coffee plantations were abandoned for economic reasons in the middle of the 20th century. Coffee species (Coffea arabica, C. canephora and C. liberica) were introduced from Africa in the late 19th century, they survived in the wild and spontaneously cross-hybridized. Coffee species were originally planted in native forest in association with leguminous trees (mostly introduced species) to improve their growth. Thus the canopy cover over rustic shade coffee plantations is heterogeneous with a majority of large crowns, attributed to leguminous trees. The aim of this study was to identify suitable areas for coffee inter-specific hybridization in New Caledonia using field based environmental parameters and remotely sensed predictors. Due to the complex structure of tropical vegetation, remote sensing imagery needs to be spatially accurate and to have the appropriate bands for monitoring vegetation cover. Quickbird panchromatic (black and white) imagery at 0.6 to 0.7 m spatial resolutions and multispectral imagery at 2.4 m spatial resolution were pansharpened and used for this study. The two most suitable remotely sensed indicators, canopy heterogeneity and tree crown size, were acquired by the sequential use of tree crown detection (neural network), image processing (such as textural analysis) and classification. All models were supervised and trained on learning data determined by human expertise. The final model has two remotely sensed indicators and three physical parameters based on the Digital Elevation Model: elevation, slope and water flow accumulation. Using these five predictive variables as inputs, two modelling methods, a decision tree and a neural network, were implemented. The decision tree, which showed 96.9% accuracy on the test set, revealed the involvement of ecological parameters in the hybridization of Coffea species. We showed that hybrid zones could be characterized by combinations of modalities, underlining the complexity of the environment concerned. For instance, forest heterogeneity and large crown size, steep slopes (> 53.5%) and elevation between 194 and 429 m asl, are favourable factors for Coffea inter-specific hybridization. The application of the neural network on the whole area gave a predictive map that distinguished the most suitable areas by means of a nonlinear continuous indicator. The map provides a confidence level for each area. The most favourable areas were geographically localized, providing a clue for the detection and conservation of favourable areas for Coffea species neo-diversity.     

Fission Product Yields of U, U, U and Pu in Fields of Thermal Neutrons, Fission Neutrons and 14.7-MeV Neutrons

The yields of more than fifteen fission products have been carefully measured using radiochemical techniques, for ²³⁵U(n,f), ²³⁹Pu(n,f) in a thermal spectrum, for ²³³U(n,f), ²³⁵U(n,f), and ²³⁹Pu(n,f) reactions in a fission neutron spectrum, and for ²³³U(n,f), ²³⁵U(n,f), ²³⁸U(n,f), and ²³⁹Pu(n,f) for 14.7 MeV monoenergetic neutrons. Irradiations were performed at the EL3 reactor, at the Caliban and Prospero critical assemblies, and at the Lancelot electrostatic accelerator in CEA-Valduc. Fissions were counted in thin deposits using fission ionization chambers. The number of fission products of each species were measured by gamma spectrometry of co-located thick deposits.     

The necessity of sample quality assessment in 14C AMS dating: The case of Cova des Pas (Menorca – Spain)

The Cova des Pas cave is a karstic cave in the cliffs of the Barranc (canyon) de Trebalúger. It is a small cave only 6.5 m deep, 4.5 m wide and 1.7 m high. Yet more than 70 burials, in foetal position, from the Early Iron Age were found in this small cave. The conservation of the archaeological remains was very unusual. Not only wood, ropes and other plant material was found, but also remains of body tissue, hair and leather. In spite of the remarkable preservation of the bodies and artefacts, the state of conservation of the bone material was very bad. The bones contained little and heavily deteriorated collagen and the organic plant material was very fragile. The special environmental conditions of the cave are the cause of these unusual preservation conditions. Although the cave is situated in a limestone cliff, the soil of the cave is very acid. Unexpectedly bad sample quality seemed to be the major drawback for AMS radiocarbon dating on hair, wood, ropes and bone collagen, as well as on bio-apatite.     

Milk yield and composition of dairy cows fed concentrate based on naked oats.

A 1.5-yr study was designed to determine the effects of feeding isonitrogenous and isoenergetic concentrates based on naked oats, corn, or a mixture (50: 50 on as-fed basis) of naked oats and corn on milk yield and composition. In vitro dry matter (DM) digestibility and ruminal degradabilities of DM, N, and starch of naked oats were compared with those of covered oats. Twenty-seven multiparous Holstein cows were blocked by similar calving date and assigned to 9 replicates. All cows were fed a mixture of grass silage, protein supplement, concentrate, and a vitamin and mineral mix for ad libitum intake. Treatment diets were fed from 3 to 36 wk of lactation. Milk yield and composition, yield of 4% fat-corrected milk, and yield of protein and fat were similar among treatments. Ruminal effective degradabilities of DM were higher for naked oats than for covered oats, but the ruminal degradabilities of crude protein and starch were similar. The rapidly degradable fractions of DM, crude protein, and starch were greater for naked than covered oats; the potentially degradable fractions were less. In vitro DM digestibility of naked oats was higher than was that of covered oats. Naked oats may be a good alternative to corn for milk yield.     

High level communication functionalities for wireless sensor networks

In this paper we show how to establish a reliable and efficient high level communication system in a randomly deployed network of sensors equipped with directional antennas. This high level communication system enables the programming of the sensor network using high level communication functionalities without the burden of taking care of their physical capacities (low range, unidirectional links, single frequency, presence of collisions, etc.). The high level communication functionalities we offer include point-to-point communication, point-to-area communication, and one-to-all communication. The basic idea to implement this system is to simulate a virtual network that emerges from the ad-hoc network using self-organization, self-discovery and collaborative methods. We also analyse the efficiency, scalability and robustness of the proposed protocols.     

Coupling of thermoelectric modules with a photovoltaic panel for air pre‐heating and pre‐cooling application; an annual simulation

Thermoelectric (TE) modules are possible reversible pre‐cooling and pre‐heating devices for ventilation air in buildings. In this study, the opportunity of direct coupling of TE modules with photovoltaic (PV) cells is considered. This coupling is evaluated through a numerical simulation depending on the meteorological conditions of Chambéry, Alpine region in France, and on the cooling or heating use of the TE modules, through annual energy and exergy efficiencies. For the considered conditions, TE module performances are of the same order as the ones of the vapour compression heat pumps, with a TE coefficient of performance higher than 2 for low values of input DC current. The PV–TE coupling efficiency varies between 0.096 and 0.23 over the year, with an average value of 0.157. Evolutions of the exergy effectiveness of PV and TE elements follow the same trends as the corresponding energy efficiencies but with steeper variations for the coupling exergy yield that varies between 0.004 and 0.014, with an annual average value of 0.010. The direct PV–TE coupling does not seem to be a sustainable option for the summer cooling purpose particularly. A case study with indirect coupling under a warm climate is considered and shows that the use of TE devices could be efficient in housing to ensure summer thermal comfort, but the corresponding necessary PV area would induce a high investment. Copyright © 2008 John Wiley & Sons, Ltd.     

The perfectly conducting wire grating: Computation of the diffracted field from Maxwell's equations and Hamilton's canonical system

A theoretical and numerical study of the perfectly conducting wire grating is presented. For both fundamental cases of polarization, we solve the Helmholtz equation rigorously without any physical simplifying assumption. The only approximations are due to the use of numerical techniques in the integration of a differential system. The wire cross section is to a large extent arbitrary. The interest of Hamilton's canonical equations in the numerical treatment of certain practical problems is shown. No doubt, certain ideas contained herein could be adapted for solving many other problems in electromagnetic theory.     

High field stress at and above room temperature in 2.3 nm thick oxides

It was predicted recently that oxide reliability will limit the oxide scaling at about 2.4 nm and it is known that MOS devices are increasingly required to operate at elevated temperatures. It is therefore important to carefully study the oxide degradation under electrical stress in such oxides at and above room temperature. In this article, it is shown that in 2.3 nm thick oxides, the degradation can be evaluated by monitoring the gate current when the substrate is in depletion and new results are presented on the gradual degradation in these oxides.     

Ancient Analogues of Modern Cement: Calcium Hydrosilicates in Mortars and Concretes from Gallo–Roman Thermal Baths of Western France

The long-term durability of cementbased materials over periods of time not directly accessible to laboratory experiments has to be thoroughly assessed to guarantee the safety of a radioactive waste repository. In this work, archaeological mortars and concretes have been studied to check whether their use as analogues of actual technological cements used for waste disposal is possible. Samples of mortar and concrete have been collected from several Gallo-Roman thermae of western France; they were examined as petrographically thin sections with optical microscopy and were analyzed by X-ray diffraction of microsamples (10⁻³ mg) and by electron probe microanalysis. The masonry cement appears to be entirely carbonated with large voids and fissures. In contrast, the use of lime with additional crushed brick or tile for the bath structure concrete and coating mortar induced pozzuolanic reactions. Despite the fact that the matrices are essentially composed of calcium carbonate, calcium aluminosilicates with compositions close to those of hydrogrossular, hydrated calcium silicates with composition and a structure comparable with those of calcium hydrosilicate formed in modern cement, and ettringite deposits in voids of concretes could also be identified. It is suggestea that these ancient artifacts can help identify very slow processes that rule cement alteration over long periods of time. The artifacts may be considered as possible analogues of present-day materials whenever sufficient care is taken in interpreting and extrapolating data.