636 research outputs found
Mission de reconnaissance des palmeraies du Nord-Niger. Compte-rendu de la phase I. Massif de l'Aïr (période du 16 février au 30 mars 1986)
Projet FED "VallĂ©es de l'AĂŻr". NÂŒ 51300 33.40.3
Mission de reconnaissance des palmeraies du Nord Niger. Compte-rendu de mission (suite de la Phase I). PĂ©riode du 23 au 29 mai 1986
Projet F.E.D. "VallĂ©es de l'AĂŻr" - NÂŒ 51300 33.40.3
Mission de reconnaissance des palmeraies du Nord-Niger. Identification de la production dattiĂšre (Suite de la Phase I). PĂ©riode du 2 au 26 juillet 1986
Projet FED "VallĂ©es de l'AĂŻr -NÂŒ 51300-33.40.34". Rapport nÂŒ
Thick films of YSZ electrolytes by dip-coating process
Yttria stabilized zirconia (YSZ, 8% Y2O3) thick films were coated on porous Ni-YSZ substrates using the dip-coating process and a suspension with a new formulation. The
suspension was obtained by addition of a polymeric matrix in a stable suspension of a commercial YSZ (Tosoh) powders dispersed in an azeotropic MEK-EtOH mixture. The green layers were densified after an optimization of the suspension composition. YSZ Tosoh particles encapsulated by a zirconium alkoxide sol and added with colloidal alkoxide
precursor are used to load the suspension. The in situ growth of these colloids increases significantly the layers density after an appropriated heat treatment. The obtained films are continuous, homogeneous and 20 ÎŒm thick. Different microstructures are obtained depending on the synthesis parameters of the suspension
Simulating temporal evolution of pressure in two-phase flow in porous media
We have simulated the temporal evolution of pressure due to capillary and
viscous forces in two-phase drainage in porous media. We analyze our result in
light of macroscopic flow equations for two-phase flow. We also investigate the
effect of the trapped clusters on the pressure evolution and on the effective
permeability of the system. We find that the capillary forces play an important
role during the displacements for both fast and slow injection rates and both
when the invading fluid is more or less viscous than the defending fluid. The
simulations are based on a network simulator modeling two-phase drainage
displacements on a two-dimensional lattice of tubes.Comment: 12 pages, LaTeX, 14 figures, Postscrip
Immigrant community integration in world cities
As a consequence of the accelerated globalization process, today major cities
all over the world are characterized by an increasing multiculturalism. The
integration of immigrant communities may be affected by social polarization and
spatial segregation. How are these dynamics evolving over time? To what extent
the different policies launched to tackle these problems are working? These are
critical questions traditionally addressed by studies based on surveys and
census data. Such sources are safe to avoid spurious biases, but the data
collection becomes an intensive and rather expensive work. Here, we conduct a
comprehensive study on immigrant integration in 53 world cities by introducing
an innovative approach: an analysis of the spatio-temporal communication
patterns of immigrant and local communities based on language detection in
Twitter and on novel metrics of spatial integration. We quantify the "Power of
Integration" of cities --their capacity to spatially integrate diverse
cultures-- and characterize the relations between different cultures when
acting as hosts or immigrants.Comment: 13 pages, 5 figures + Appendi
Dartmoor Payment-By-Results T&T2: final report (15A)
The proposal of the second Dartmoor Test & Trial (T & T) was to test the practical development of payment by results (PBR) on common land by designing and trialling a model with commons graziers across the varied landscape of Dartmoor. It aimed to better understand the barriers and opportunities to improve delivery, including the necessary governance. Both the reward (payment for delivery) and governance and financial administration were addressed
Natural recovery of genetic diversity by gene flow in reforested areas of the endemic Canary Island pine, Pinus canariensis
The endemic pine, Pinus canariensis, forms one of the main forest ecosystems
in the Canary Islands. In this archipelago, pine forest is a mosaic of natural
stands (remnants of past forest overexploitation) and artificial stands planted
from the 1940's. The genetic makeup of the artificially regenerated forest is
of some concern. The use of reproductive material with uncontrolled origin or
from a reduced number of parental trees may produce stands ill adapted to local
conditions or unable to adapt in response to environmental change. The genetic
diversity within a transect of reforested stands connecting two natural forest
fragments has been studied with nuclear and chloroplast microsatellites. Little
genetic differentiation and similar levels of genetic diversity to the
surrounding natural stands were found for nuclear markers. However, chloroplast
microsatellites presented lower haplotype diversity in reforested stands, and
this may be a consequence of the lower effective population size of the
chloroplast genome, meaning chloroplast markers have a higher sensitivity to
bottlenecks. Understory natural regeneration within the reforestation was also
analysed to study gene flow from natural forest into artificial stands.
Estimates of immigration rate into artificially regenerated forest were high
(0.68-0.75), producing a significant increase of genetic diversity (both in
chloroplast and nuclear microsatellites), which indicates the capacity for
genetic recovery for P. canariensis reforestations surrounded by larger natural
stands
Ground State Structure in a Highly Disordered Spin Glass Model
We propose a new Ising spin glass model on of Edwards-Anderson type,
but with highly disordered coupling magnitudes, in which a greedy algorithm for
producing ground states is exact. We find that the procedure for determining
(infinite volume) ground states for this model can be related to invasion
percolation with the number of ground states identified as , where
is the number of distinct global components in the
``invasion forest''. We prove that if the invasion
connectivity function is square summable. We argue that the critical dimension
separating and is . When , we consider free or periodic boundary conditions on cubes of
side length and show that frustration leads to chaotic dependence with
{\it all} pairs of ground states occuring as subsequence limits. We briefly
discuss applications of our results to random walk problems on rugged
landscapes.Comment: LaTex fil
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