7,079 research outputs found
Metastability at the Yield-Stress Transition in Soft Glasses
We study the solid-to-liquid transition in a two-dimensional fully periodic
soft-glassy model with an imposed spatially heterogeneous stress. The model we
consider consists of droplets of a dispersed phase jammed together in a
continuous phase. When the peak value of the stress gets close to the yield
stress of the material, we find that the whole system intermittently tunnels to
a metastable "fluidized" state, which relaxes back to a metastable "solid"
state by means of an elastic-wave dissipation. This macroscopic scenario is
studied through the microscopic displacement field of the droplets, whose time
statistics displays a remarkable bimodality. Metastability is rooted in the
existence, in a given stress range, of two distinct stable rheological branches
as well as long-range correlations (e.g., large dynamic heterogeneity)
developed in the system. Finally, we show that a similar behavior holds for a
pressure-driven flow, thus suggesting possible experimental tests.Comment: 13 pages, 11 figure
A 10 year review of the number of bovine dairy holdings and the dairy bovine population on the Maltese Islands
The process of identification and registration of bovines and bovine holdings on the Maltese Islands has been computerised since 2002, with the introduction of the National Livestock Database of Malta. This is a computerised and centralised system which has made collection, management and analysis of data possible. The aims of this paper were to study in detail ten year trends in the number of bovine dairy holdings together with the bovine population on these holdings and to compare these trends with those reported in other European countries. Six trends related to the number of bovine dairy holdings and their bovine population were analysed in the study. The general trends showed that there was a significant decrease in the number of dairy holdings, in the bovine population and in the number of female bovines greater than 2 years of age during the study period. The average herd size and the average number of females greater than 2 years of age on the dairy holdings showed no statistically significant changes. On the other hand, a significant increase in the ratio of female to male bovines was registered on these holdings.peer-reviewe
From failure to value: Economic valuation for a selected set of products and services from Mediterranean forests
Aim of study: the paper estimates the economic value of a selected range of forest products and services, i.e. roundwood, nonwood
forest products (NWFPs), and carbon-related services.
Area of study: the research covers 21 Mediterranean countries, distinguished into four sub-regions.
Material and methods: data have been gathered from official statistical sources (e.g. FAOSTAT), scientific literature and technical
reports. Different estimation approaches based on market-price have been used for different products/services.
Main results: the estimated value ranges between \u20ac10,512 and \u20ac11,158 million (M). Wood products represent more than 85% of
the total value. Within them, industrial timber is the most relevant component (65%). Figures for NWFPs are likely to be underestimated
because data are available only for some products and countries. When using alternative estimates for pine nuts, pine resin
and cork, figures show a \u20ac36.8-572 M increase. In geographical terms, the economic value of Mediterranean forests is highly
concentrated: North-West Mediterranean countries account for 70%, and nearly 90% is in just four countries (France, Spain, Turkey
and Italy).
Research highlights: enhancing the offer of Mediterranean forest products and increasing their role in the rural economy could
help to reduce the costs of forest protection: a well-structured forest economy ensuring stable flows of incomes can provide a fundamental
set of public non-market services and social values to both local people and the whole community. Understanding the true
value of natural resources, then, is an essential step for promoting their protection and sustainable use
Fluidisation and plastic activity in a model soft-glassy material flowing in micro-channels with rough walls
By means of mesoscopic numerical simulations of a model soft-glassy material,
we investigate the role of boundary roughness on the flow behaviour of the
material, probing the bulk/wall and global/local rheologies. We show that the
roughness reduces the wall slip induced by wettability properties and acts as a
source of fluidisation for the material. A direct inspection of the plastic
events suggests that their rate of occurrence grows with the fluidity field,
reconciling our simulations with kinetic elasto-plastic descriptions of jammed
materials. Notwithstanding, we observe qualitative and quantitative differences
in the scaling, depending on the distance from the rough wall and on the
imposed shear. The impact of roughness on the orientational statistics is also
studied
Convergence of the one-dimensional Cahn-Hilliard equation
We consider the Cahn-Hilliard equation in one space dimension with scaling a
small parameter \epsilon and a non-convex potential W. In the limit \espilon
\to 0, under the assumption that the initial data are energetically
well-prepared, we show the convergence to a Stefan problem. The proof is based
on variational methods and exploits the gradient flow structure of the
Cahn-Hilliard equation.Comment: 23 page
An approach to model interest for planetary rover through Dezert-Smarandache Theory
In this paper we propose an approach for assigning an interest level to the goals of a planetary rover. Assigning an interest level to goals, allows the rover to autonomously transform and reallocate the goals. The interest level is defined by data-fusing payload and navigation information. The fusion yields an "interest map", that quantifies the level of interest of each area around the rover. In this way, the planner can choose the most interesting scientific objectives to be analyzed, with limited human intervention, and reallocates its goals autonomously. The Dezert-Smarandache Theory of Plausible and Paradoxical Reasoning was used for information fusion: this theory allows dealing with vague and conflicting data. In particular, it allows us to directly model the behaviour of the scientists that have to evaluate the relevance of a particular set of goals. The paper shows an application of the proposed approach to the generation of a reliable interest map
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