9,214 research outputs found
On the minimum orbital intersection distance computation: a new effective method
The computation of the Minimum Orbital Intersection Distance (MOID) is an
old, but increasingly relevant problem. Fast and precise methods for MOID
computation are needed to select potentially hazardous asteroids from a large
catalogue. The same applies to debris with respect to spacecraft. An iterative
method that strictly meets these two premises is presented.Comment: 13 pages, 10 figures, article accepted for publication in MNRA
Impact of HydroPolymers on the soil biological components in mediterranean drylands
Soil degradation affects more than 52 million ha of land in counties of the European Union. This problem is
particularly serious in Mediterranean areas, where the effects of anthropogenic activities (tillage on slopes,
deforestation, and pasture production) add to problems caused by prolonged periods of drought and intense and
irregular rainfall.
Soil microbiota can be used as an indicator of the soil healthy in degraded areas. This is because soil microbiota
participates in the cycle elements and in the organic matter decomposition. All this helps to the young plants
establishment and in long term protect the soils against the erosion. During dry periods in the Mediterranean areas,
the lack of water entering the soil matrix leads to a loss of soil microbiological activity and it turns into a lower
soil production capabilities.
Under these conditions, the aim of this study was to evaluate the positive effect on soil biological components
produced by an hydro absorbent polymer (Terracottem).
The aim of the experiment was to evaluate the impact assessment of an hydropolymer (Terracottem) on the soil
biological components.
An experimental flowerpot layout was established in June 2015 and 12 variants with different amount of
Terracottem were applied as follow: i) 3.0 kg.m3 ; ii) 1.5 kg.m3 and; iii) 0 kg.m3. In all the variants were tested
the further additives: a) 1% of glucose, b) 50 kg N.ha-1 of Mineral nitrogen, c) 1% of Glucose + 50 kg N.ha-1 of
Mineral nitrogen d) control (no additive). According to natural conditions, humidity have been kept at 15% in all
the variants.
During four weeks, mineral nitrogen leaching and soil respiration have been measured in each flowerplot.
Respiration has been quantified four times every time while moistening containers and alkaline soda lime has been
used as a sorbent. The amount of CO 2 increase has been measured with the sorbent. Leaching of mineral nitrogen
has been quantified by ion exchange resins (IER). IER pouches have been placed on the bottom of each container,
and after completion of the experiment mineral nitrogen leaching has been evaluated by distillation and titration
method.
Results from respiration have shown statistically significant differences between the variants. According to
control, soil with polymers have shown significant difference when comparing respiration with independence of
the additive used. CO 2 production in the first week has exceeded the sum of the outputs of the following weeks.
Mineral nitrogen leaching measurement has shown statistically significant differences. The lowest leaching has
been occurred in control variant, while the highest in variant containing only the addition of mineral nitrogen.
Research results may conclude that the biological part of the test soil is not limited by a lack of components, the
only thing that suppresses its activity is the lack of moisture. After moistening it leads to a rapid growth of soil
activity, without causing the nutrients loss. Besides, Terracottem has affected soil activity neither positively nor
negatively, but it considers being a suitable tool for reducing the drought impact in arid and semi-arid areas.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Exponential wealth distribution in a random market. A rigorous explanation
In simulations of some economic gas-like models, the asymptotic regime shows
an exponential wealth distribution, independently of the initial wealth
distribution given to the system. The appearance of this statistical
equilibrium for this type of gas-like models is explained in a rigorous
analytical way.Comment: 9 pages, 4 figure
Exponential wealth distribution: a new approach from functional iteration theory
Exponential distribution is ubiquitous in the framework of multi-agent
systems. Usually, it appears as an equilibrium state in the asymptotic time
evolution of statistical systems. It has been explained from very different
perspectives. In statistical physics, it is obtained from the principle of
maximum entropy. In the same context, it can also be derived without any
consideration about information theory, only from geometrical arguments under
the hypothesis of equiprobability in phase space. Also, several multi-agent
economic models based on mappings, with random, deterministic or chaotic
interactions, can give rise to the asymptotic appearance of the exponential
wealth distribution. An alternative approach to this problem in the framework
of iterations in the space of distributions has been recently presented.
Concretely, the new iteration given by . It is found that the
exponential distribution is a stable fixed point of the former functional
iteration equation. From this point of view, it is easily understood why the
exponential wealth distribution (or by extension, other kind of distributions)
is asymptotically obtained in different multi-agent economic models.Comment: 6 pages, 5 figure
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